KR101241879B1 - method for transmitting and receiving data using a plurality of carrier - Google Patents

Abstract

The present invention relates to a data transmission / reception method in a mobile communication system, and more particularly, to a data transmission / reception method in an orthogonal frequency division multiple access (OFDMA) mobile communication system. In a method of transmitting data using a plurality of subcarriers according to an embodiment of the present invention, in a method of transmitting arbitrary data symbols by a plurality of subcarriers, multicast / broadcast data and unicast data to be transmitted Obtaining a; And multiplexing the multicast / broadcast data and unicast data and transmitting them in units of radio frames including at least one data symbol.

OFDM, OFDMA, MBMS, Unicast

Description

Method for transmitting and receiving data using a plurality of carriers

1A is a diagram illustrating an RF combined reception method used in an embodiment of the present invention.

FIG. 1B is a diagram illustrating a method of transmitting and receiving multicast / broadcast data and unicast data through different radio frames according to one embodiment of the present invention.

FIG. 2A is a diagram illustrating a method of multiplexing multicast / broadcast data and unicast data into one radio frame by FDM and transmitting and receiving. FIG.

2B is a diagram illustrating a method of multiplexing multicast / broadcast data and unicast data into one radio frame by TDM and transmitting and receiving.

FIG. 2C is a diagram illustrating a method of multiplexing and transmitting multicast / broadcast data and unicast data in one radio frame by using a multiplexing with frequency-time scheme.

3A to 3B illustrate an example of a modification of the transmission and reception method according to FIG. 2.

4A to 4D illustrate the advantages of the transmission and reception method proposed by the present invention.

5 is a diagram illustrating an OFD symbol on which a synchronization channel is transmitted.

The present invention relates to a data transmission / reception method in a mobile communication system, and more particularly, to a data transmission / reception method in an orthogonal frequency division multiple access (OFDMA) mobile communication system.

Hereinafter, orthogonal frequency division multiplexing (OFDM) will be described. The basic principle of OFDM is to divide a high-rate data stream into a large number of low-rate data streams, which are transmitted simultaneously using multiple carriers. Each of the plurality of carriers is called a subcarrier. Since orthogonality exists between the multiple carriers of the OFDM, the frequency components of the carriers can be detected at the receiving end even if they overlap each other. The high data rate data stream is converted into a plurality of low data rate data streams through a serial to parallel converter, and each subcarrier is included in the parallel data streams. After multiplying, the respective data strings are summed and sent to the receiving end.

Hereinafter, orthogonal frequency division multiple access (OFDMA) will be described. OFDMA refers to a multiple access method for realizing multiple access by providing each user with a part of subcarriers available in a system using OFDM as a modulation method. OFDMA provides each user with a frequency resource called a subcarrier, and each frequency resource is provided to a plurality of users independently of each other so that they do not overlap each other. After all, frequency resources are allocated mutually exclusive.

Hereinafter, a data transmission / reception method in the communication system using the above-described OFDMA will be described. In a cellular mobile communication system using OFDMA as a multiple access method for downlink data transmission, when neighboring multicast / broadcast data is transmitted on the downlink, multiple neighbor cells transmit the same data. can do.

The multicast / broadcast data refers to data transmitted to at least one terminal in a mobile communication system. In addition, the multicast / broadcast data is transmitted from a plurality of cells and transmitted to a plurality of terminals, and the plurality of cells transmit the same data to the terminal. The terminal receives signals from a plurality of cells and can perform combined reception on the multicast / broadcast data in the RF combining method described below. From the user's point of view, the multicast / broadcast data refers to data provided to a plurality of users. Thus, multiple cells provide the same data to the multiple users. When the multicast / broadcast data is transmitted in the communication system, the same data sent by neighboring cells in the receiving terminal is controlled by controlling a transmission method of cells neighboring the cell transmitting the data. Combination and demodulation allow greater reception energy and multi-cell diversity gains.

As a coupling scheme in the receiver for the same data transmitted by a plurality of cells, an RF (Radio Frequency) coupling scheme may be used. In order to perform the RF combining scheme, the cells transmitting the combining data must finally transmit the same modulation symbol to the same frequency-time domain at the end of the transmitting end. In this case, the receiving terminal can demodulate as if a signal transmitted by one cell is received in a multipath via different radio channel paths without having to separately distinguish the same data signals received in multiple cells.

In addition, a predetermined pilot symbol may be transmitted between the cell and the mobile terminal in order to assist in demodulation of the mobile terminal which is combined and received by the RF combining method. Pilots to assist the demodulation are the same for multiple cells, and the pilots are sent in the same frequency-time domain. In this case, the mobile terminal can perform channel estimation by demodulating like a pilot received in one cell without separately receiving and receiving pilot symbols transmitted by each cell.

An additional description of the RF coupling scheme is as follows. In a cellular mobile communication system using a multi-carrier multiple access technique, when all cells are synchronized, a user may obtain diversity gain by demodulating a plurality of combined signals received from multiple cells through an OFDM receiver without special processing. (RF combined reception method). In this method, the same code is used for signals received from several cells, and the maximum gain can be obtained only when the transmission methods, patterns, and positions of the pilots are identical. 1A is a diagram illustrating an RF combined reception method used in an embodiment of the present invention. It is preferable to set the length of the guard interval so that each time delay in FIG. 1A can be located within a guard interval (GI).

However, a cellular mobile communication system using OFDMA as a multiple access method for downlink data transmission can transmit unicast data in downlink in addition to multicast / broadcast data. In this case, a cell other than the cell transmitting the unicast data does not transmit the data.

The unicast data refers to data transmitted to one mobile terminal in a mobile communication system. In addition, the unicast data may be transmitted from a specific cell and transmitted to one terminal belonging to the specific cell. From the user's point of view, the unicast data refers to data provided to a particular user. Thus, one particular cell will transmit unicast data to a particular user.

When the unicast data is transmitted in the cellular mobile communication system, that is, when unicast data is transmitted from each cell to specific terminals belonging to the cell, the specific cell transmitting the unicast data is transmitted. The pilot signal and data to be distinguished from the pilot signal and data transmitted from other cells. As described above, the pilot signal and the data signal should be distinguished from each other between the cells from the transmission side, and the reception side should distinguish the pilot signal and the data from each other so that correct data reception is possible.

As described above, the cellular mobile communication system must process both multicast / broadcast data and unicast data having different conditions required for correct data reception.

The present invention has been proposed to improve the performance of a communication system that processes multicast / broadcast data and unicast data as described above. An object of the present invention is to provide a radio resource for multicast / broadcast data and unicast data. It is to provide a method for transmitting and receiving by minimizing waste.

summary

In a method of transmitting data using a plurality of subcarriers according to an embodiment of the present invention, in a method of transmitting arbitrary data symbols by a plurality of subcarriers, multicast / broadcast data and unicast data to be transmitted Obtaining a; And multiplexing the multicast / broadcast data and unicast data and transmitting them in units of radio frames including at least one data symbol.

In addition, the method for receiving data using a plurality of subcarriers according to an embodiment of the present invention, in the method for receiving arbitrary data symbols transmitted by the plurality of subcarriers, multicast / broadcast data and Receiving a signal multiplexed with unicast data in units of radio frames consisting of at least one data symbol; And obtaining the multicast / broadcast data and unicast data from the received signal.

In addition, a data frame according to an embodiment of the present invention includes a multicast / broadcast data and unicast data to be transmitted in a data frame including at least one data symbol, wherein each data is included in the data symbol. The data symbol is transmitted by using a plurality of subcarriers, characterized in that the data symbols are transmitted by a plurality of subcarriers.

Work according to the invention Example

According to another embodiment of the present invention, a data transmission / reception method includes multicast / broadcast data transmitted in a plurality of cells in a cellular mobile communication system using OFDMA and unicast data transmitted to a specific terminal for each cell. There is a feature that minimizes the associated signaling and frequency-time resource waste required when transmitting in combination.

One embodiment of the present invention includes an invention relating to a communication system for processing multicast / broadcast data and unicast data together. Hereinafter, a method of multiplexing and transmitting multicast / broadcast data and unicast data according to an embodiment of the present invention is proposed.

First Embodiment

An embodiment of the present invention proposes a method of transmitting and receiving multicast / broadcast data and unicast data. The multiplexing method used by an embodiment of the present invention may perform multiplexing on a specific radio frame basis or multiplex the multicast / broadcast data and unicast data within a specific radio frame. have. The radio frame represents a basic unit for transmitting data in the cellular mobile communication system, and the present invention is not limited to the above-mentioned name.

1B is a diagram illustrating one of the multiplexing methods proposed by an embodiment of the present invention. As shown in FIG. 1B, multicast / broadcast data and unicast data are transmitted through different radio frames, respectively. That is, the specific radio frame can transmit only multicast / broadcast data, and the specific radio frame can transmit only unicast data. The mobile terminal receives the radio frame from the cellular mobile communication system, and the data transmitted in a specific radio frame (that is, a radio frame for transmitting multicast / broadcast data) are combined and received by the above-described RF combining method, For data transmitted in another radio frame, a signal may be decoded by receiving a signal from a specific cell. The first multiplexing method described above has an advantage of using a relatively simple algorithm because data is classified and transmitted according to a radio frame.

2A to 2C are diagrams illustrating another one of the transmission and reception methods proposed by one embodiment of the present invention. The second method illustrated in FIGS. 2A to 2C is a method in which multicast / broadcast data and unicast data are transmitted and received in the same radio frame. The above-described transmission / reception method may use various multiplexing methods such that the multicast / broadcast data and the unicast data are received separately in one radio frame. For example, the transmission / reception method may include a time division multiplex (TDM) method for dividing the multicast / broadcast data and unicast data according to a transmission time, and a frequency for transmitting the multicast / broadcast data and unicast data. Frequency division multiplex (FDM) method for classifying by region, frequency-time multiplexing method for classifying the multicast / broadcast data and unicast data in consideration of the frequency domain and time to be transmitted together Can be used.

2A is a diagram illustrating a method of multiplexing multicast / broadcast data and unicast data into one radio frame by using the above-described FDM scheme and transmitting and receiving the same. The radio frame is preferably transmitted including a specific pilot signal. More preferably, the pilot signal transmits a predetermined signal between the mobile communication system and the mobile terminal to enable the mobile terminal to estimate a channel, and includes multicast / broadcast data included in a specific radio frame. Or control information indicating which part of the total data transmitted to the mobile terminal belongs to the unicast data. The mobile station can receive the pilot to estimate the channel for multicast / broadcast data received from a plurality of cells, and can successfully demodulate the data by performing the RF combined reception described above. In addition, the mobile terminal may receive the pilot to know that the unicast data received from a specific cell is data transmitted to the mobile station, and may perform channel estimation for receiving the unicast data. Although FIG. 2A illustrates an example in which a pilot signal is transmitted in the first OFDM symbol of a specific radio frame, this is only an example for explaining the present embodiment. According to the present invention, there is no limitation in a frequency band or time period in which the pilot signal is transmitted, and a pilot signal may be transmitted in an arbitrary OFDM symbol, and may be transmitted only by some subcarriers even within a specific OFDM symbol. have. 3A is a diagram illustrating multiplexing of the above-described FDM scheme, and as shown, it can be seen that pilot signals are transmitted through various frequency-time domains. The multiplexing of the above-described FDM scheme may be applied in a different manner for each radio frame. That is, as illustrated in FIG. 2A, the frequency domains of the multicast / broadcast data transmitted by the first radio frame and the second radio frame may be different from each other.

FIG. 2B is a diagram illustrating a method of multiplexing multicast / broadcast data and unicast data into one radio frame and transmitting and receiving by the above-described TDM scheme. Preferably, the radio frame is transmitted including a specific pilot signal, and the pilot signal transmits a predetermined signal between the mobile communication system and the mobile terminal to enable the mobile terminal to estimate a channel. More preferably, the multicast / broadcast data or unicast data included in a specific radio frame may further include control information indicating which part of the total data transmitted to the mobile terminal belongs. The mobile terminal can receive the pilot to estimate the channel for multicast / broadcast data received from a plurality of cells, and can successfully demodulate the data by performing the above RF combined reception. In addition, the mobile terminal may receive the pilot to know that the unicast data received from a specific cell is data transmitted to the mobile station, and may perform channel estimation for receiving the unicast data. Although FIG. 2B illustrates an example in which a pilot signal is transmitted in the first OFDM symbol of a specific radio frame, this is only an example for explaining the present embodiment. 3B is a diagram illustrating multiplexing of the above-described TDM scheme, and as shown, it can be seen that pilot signals are transmitted through various frequency-time domains. The multiplexing of the above-described TDM scheme may be applied in a different manner for each radio frame. That is, as illustrated in FIG. 2A, time intervals of the multicast / broadcast data transmitted by the first radio frame and the second radio frame may be different from each other.

FIG. 2C is a diagram illustrating a method of multiplexing and transmitting multicast / broadcast data and unicast data in one radio frame by the aforementioned multiplexing with frequency-time scheme. The multicast / broadcast data and unicast data are transmitted by being divided into specific frequency domains and time domains. The multiplexing method of FIG. 2C shows an example of multiplexing with a certain hopping pattern. Preferably, the hopping pattern for multiplexing is provided to both the mobile communication system and the mobile terminal, and frequency-time diversity can be obtained by appropriately controlling the hopping pattern. The data of FIG. 2C also preferably includes a specific pilot signal. Although FIG. 2C illustrates an example in which a pilot signal is transmitted in the first OFDM symbol of a specific radio frame, this is only an example for describing the present embodiment. According to the present invention, there is no limitation in a frequency band or time period in which the pilot signal is transmitted, and a pilot signal may be transmitted in an arbitrary OFDM symbol, and may be transmitted only by some subcarriers even within a specific OFDM symbol. have. The hopping pattern described above can be included in each radio frame. That is, as illustrated in FIG. 2A, the time-frequency region of the multicast / broadcast data transmitted by the first radio frame and the second radio frame may be different.

The above-described multiplexing method of TDM, FDM, and frequency-time multiplexing has an advantage of superior flexibility compared to the multiplexing method of FIG. 1B. Especially in the case of FDM, there are additional advantages. 4 illustrates the advantages of FDM multiplexing proposed by the present invention. Hereinafter, an additional advantage of FDM multiplexing will be described with reference to FIG. 4. 4a shows a structure of a radio frame according to a TDM multiplexing scheme. If the mobile communication system transmits a signal by separately configuring the pilot signals for the unicast data and the multicast / broadcast data, the TDM scheme is applied to the entire frequency band for the subcarrier on which the data is transmitted. You should include a pilot signal for Of course, the pilot signal is not to be included only in a specific OFDM symbol (first and second OFDM symbols in the figure), as shown in the specific Figure 4a, nor is it included for all subcarriers (subcarriers). However, for accurate channel estimation and data demodulation, it may be desirable for the pilot signal to be distributed throughout the frequency band of the subcarrier. Therefore, the TDM scheme preferably includes a pilot signal over a wide frequency band.

However, the FDM scheme has additional advantages over other schemes in pilot signals. 4b shows a structure of a radio frame according to the FDM scheme. As described above, if the mobile communication system transmits signals by separately configuring the pilot signals for the unicast data and the multicast / broadcast data, the FDM scheme adds additional pilot signals for specific data to the specific data. It can be included only in the frequency band in which is transmitted. Since channel estimation and data demodulation for the specific data are limited to a constant band in which the specific data is transmitted, the pilot signal for the predetermined band can be included and transmitted. Therefore, there is an advantage that efficient data demodulation is possible with only a relatively small pilot signal.

The specific data may be various kinds of data, and may be unicast data or multicast / broadcast data. 4A and 4B illustrate a case in which a pilot signal for unicast data is included and an additional pilot signal for a file for the multicast / broadcast data is included. By using the additional pilot, the mobile terminal can receive the multicast / broadcast data combined by the RF combining method. That is, signaling including control information on frequency / time / code resource allocation and allocation of multicast / broadcast data may be applied to unicast data in the same manner. In the case of unicast data, if an ID of a terminal allocated with a resource in each radio frame and a resource allocated to the ID are transmitted through downlink signaling, the multicast / broadcast data is transmitted in each radio frame. The ID for identifying the service type of multicast / broadcast and resource allocation according to the ID may be transmitted in downlink signaling. As a result, while using the same signaling for multicast / broadcast data and unicast data, the ID information of the terminal can be replaced with an ID for distinguishing a service type of the multicast / broadcast. In conclusion, when using the transmission and reception method according to an embodiment of the present invention, the mobile terminal has an advantage of receiving multicast / broadcast data in the same manner as when receiving unicast data.

The radio frame is generally divided into relatively small time units, and since a change in channel will be relatively small while one radio frame is transmitted, the pilot is applied to a specific OFDM symbol as shown in FIG. 4A or 4B. You can include a signal. However, this is only an embodiment of the present invention and the present invention is not limited thereto. That is, a radio frame according to the multiplexing scheme of the present invention may include pilot signals in various frequency-time domains. 4C and 4D show that the pilot signal is located in various frequency-time domains. As shown, the pilot signal may be transmitted through various OFDM symbols without being limited to a specific frequency domain or time. In addition, the additional pilot signal may be provided for combined reception of multicast / broadcast data, and is preferably transmitted in the frequency-time domain in which the multicast / broadcast data is transmitted. There is no limitation in the frequency-time domain in which the additional pilot signal is transmitted. Therefore, various pilot signals may be configured as shown in FIG. 4C or 4D.

Second Embodiment

Hereinafter, a method of scheduling multicast / broadcast data and unicast data according to an embodiment of the present invention will be described. Hereinafter, two scheduling methods according to an embodiment of the present invention are proposed. Hereinafter, the 'radio frame in which multicast / broadcast data is transmitted' refers to a radio frame in which not only a radio frame transmitting only multicast / broadcast data but also multiplexed and transmitted to the unicast data, and the multicast / broadcast It refers to a radio frame in which cast data can be multiplexed and transmitted.

The first scheduling method proposed according to an embodiment of the present invention is a method of transmitting multicast / broadcast in a specific radio frame according to a predetermined pattern. This pattern may be periodic on the time axis or follow a specific rule. Also, in a mobile communication system, the mobile terminal may inform the mobile terminal of this pattern in advance so that the terminal may multicast / receive only in a radio frame corresponding to the pattern. It can be seen that broadcast data can be received. This method allows a terminal to receive multicast / broadcast data only in a predetermined radio frame without having to check whether multicast / broadcast data is received every radio frame. The terminal receiving the bay has an advantage of minimizing battery consumption required for data reception.

In the first scheduling method, the mobile communication system does not necessarily need to transmit multicast / broadcast data in a radio frame allocated for multicast / broadcast data transmission, and transmits the corresponding radio frame. Whether the multicast / broadcast data is actually transmitted in the current radio frame or the amount of multicast / broadcast data transmitted in the current radio frame, or multiplexing to control information transmitted through the control information. Information), the mobile terminal can read this control information and receive the necessary multicast / broadcast data. In addition, when an additional pilot for multicast / broadcast data demodulation is used in a radio frame in which multicast / broadcast data is transmitted, multicast is included in control information of the radio frame. Additional control information indicating whether or not to use additional pilots for broadcast and type of pilot used, structure, and the like is included.

As mentioned above, the pattern may be periodic or aperiodic. For example, the radio frame in which the multicast / broadcast data is transmitted may be an odd numbered radio frame. As described above, the radio frame in which the multicast / broadcast data is transmitted may include only multicast / broadcast data, or may be multiplexed with unicast data in a specific manner, and the multicast / broadcast data Not only may include, but may not actually include multicast / broadcast data. In addition, the specific multiplexing may be performed in various ways such as TDM, FDM, and multiplexing with frequency-time, and the multiplexing may be determined according to a predetermined pattern. Accordingly, according to the example, the mobile communication system multiplexes and transmits multicast / broadcast data and unicast data in an FDM scheme to odd-numbered radio frames, and the amount of multicast / broadcast data transmitted in the radio frame or Control information on whether or not multicast / broadcast data is transmitted in a radio frame can be transmitted, and the mobile station RFs a specific frequency region of an odd-numbered radio frame by using the information on the pattern already reported and the control information. The combined reception can be performed in a combined manner. The control information transmission method is not limited, and may be included in a part of the radio frame and transmitted or transmitted through a separate communication channel.

A second scheduling method according to an embodiment of the present invention is a method of multiplexing and transmitting multicast / broadcast data and unicast data through an arbitrary radio frame in the mobile communication system as needed. to be. In this scheme, even though the terminal tries to receive only the multicast / broadcast data, the terminal does not know in which radio frame the multicast / broadcast data is to be transmitted. Therefore, the terminal receives control information transmitted in each radio frame. To ensure that multicast / broadcast data is transmitted in that radio frame.

If the first scheduling method described above is static scheduling, the second scheduling method may be characterized as dynamic scheduling.

In the second method, the mobile communication system does not necessarily need to transmit multicast / broadcast data in a radio frame allocated for multicast / broadcast data transmission, but through a corresponding radio frame. Whether multicast / broadcast data is actually transmitted in the current radio frame to the transmitted control information, or the amount of multicast / broadcast data transmitted in the current radio frame, or multiplexing By including the information and transmitting it, the mobile terminal can read this control information and receive the necessary multicast / broadcast data. In addition, when an additional pilot for multicast / broadcast data demodulation is used in a radio frame in which multicast / broadcast data is transmitted, control information of the radio frame includes multicast / broadcast. Additional control information indicating whether or not to use the additional pilot for the pilot type, structure, etc. may be included. The control information transmission method is not limited, and may be included in a part of the radio frame and transmitted or transmitted through a separate communication channel.

Third Embodiment

Hereinafter, a method of controlling signaling regarding a transmission format of a radio frame according to an embodiment of the present invention will be described.

The mobile communication system may transmit various types of data through one or a plurality of radio frames. Hereinafter, a method of transmitting / receiving information on a transmission format of the radio frame when transmitting various types of data will be described.

There is no restriction on the type of data described above, and an example of dividing the type of data into multicast / broadcast data transmitted to a plurality of mobile terminals and unicast data transmitted to one mobile terminal will be described.

If the transmission format of a radio frame in which multicast / broadcast data is transmitted is different from a radio frame in which only unicast data is transmitted, and the mobile terminal does not know a different transmission format in advance, the radio frame There may be a case that even the control information transmitted through) is not properly received. The transmission format means information indicating an attribute of the radio frame, such as control information about the number of OFDM symbols included in the transmitted radio frame or cyclic prefix or control information about the pilot signal. do. In addition, the radio frame in which the multicast / broadcast data is transmitted means a radio frame in which not only a radio frame transmitting only multicast / broadcast data but also multiplexed and transmits the unicast data. It means a radio frame that can be transmitted by multiplexing the broadcast data. The concept of the cyclic prefix is as follows. Inter-symbol interference can be reduced by inserting a guard interval longer than the delay spread of the channel between OFDM symbols. In addition, if a part of the OFDM signal is copied to the guard interval and placed at the beginning of the symbol, the OFDM symbol may be cyclically extended to protect the symbol. As described above, a portion disposed at the beginning of a symbol by copying a portion of the signal is called a cyclic prefix.

Hereinafter, a case in which control information as well as data included in the radio frame is not received will be described. E.g. In a radio frame in which the multicast / broadcast data is transmitted, a different number of OFDM symbols and a length of a cyclic prefix may be used as in a radio frame in which only unicast data is transmitted. As another example, in a radio frame in which the multicast / broadcast data is transmitted, a pilot of a structure used in a radio frame in which only unicast data is transmitted is not used, and only a pilot of another structure is used. Can be used. In the above-described case, if the mobile terminal does not know the transmission format for the changed radio frame, the mobile terminal not only contains data included in the radio frame, but also basic control information included in the radio frame. Even can not receive correctly.

Hereinafter, a method of transmitting control information about a transmission format of the radio frame according to an embodiment of the present invention will be described. According to an embodiment of the present invention, the mobile communication system may transmit and receive control information about a current radio frame in advance in a previous radio frame. The mobile communication system includes control information regarding a transmission format of a current radio frame in control information through a previous radio frame of a radio frame in which the multicast / broadcast data is transmitted. The control information may include information indicating that the next radio frame is a radio frame through which multicast / broadcast data is transmitted, information indicating that the next radio frame is transmitted in a different transmission format than before, or an indicator indicating a transmission format of the next radio frame ( indicator) information can be included. As described above, the information about the transmission format includes control information about the pilot, and the control information about the transmission format includes the type, size, configuration method, etc. of the pilot used for the next radio frame. It can contain a variety of information. The mobile terminal can correctly receive the next radio frame by acquiring the transmission format of the next radio frame by reading the control information about the transmission format.

As described above, the method of previously notifying the mobile terminal of the control information about the transmission format of the radio frame which is different from each other through the control information of the previous radio frame is not only used for the radio frame for transmitting the multicast / broadcast data. It is generally applicable when a transmission format of two or more radio frames is used.

Fourth Embodiment

In the above-described third embodiment, a method of transmitting and receiving control information about a transmission format of a specific radio frame has been described. Hereinafter, a method of transmitting / receiving control information regarding the transmission format when the lengths of the cyclic prefixes in the transmission formats are different will be described.

As described above, the OFDM symbol of the radio frame in which the multicast / broadcast data is transmitted may have a length of a cyclic prefix different from the OFDM symbol of the radio frame in which only unicast data is transmitted. In addition, in a mobile communication system in which OFDM symbols are transmitted through a radio frame without necessarily being related to the transmission of multicast / broadcast data and unicast data, different cyclic prefixes for each OFDM symbol are used. prefix length needs to be used. In general, the longer the length of the cyclic prefix, the higher the probability that the OFDM symbol is well protected and transmitted, and thus the quality of reception may be improved. In addition, when the length of the cyclic prefix is reduced, unnecessary overhead in the data transmission may be reduced, thereby enabling efficient communication. As described above, the mobile communication system may control the length of the cyclic prefix to improve reception quality or increase communication efficiency. For example, an OFDM symbol may be transmitted using different cyclic prefix lengths by distinguishing between a mobile terminal located at a boundary of a cell and a mobile terminal not otherwise. In addition, the OFDM symbol may be transmitted using different cyclic prefix lengths depending on whether the transmitted data is multimedia / broadcast data or unicast data. As described above, when controlling the length of the cyclic prefix, the overall performance of the mobile communication system can be improved. Hereinafter, when various cyclic prefix lengths are used, control information regarding the transmission format of the radio frame can be transmitted and received. How to do it.

The control information transmission / reception method according to an embodiment of the present invention may be based on a method of previously notifying the terminal of control information regarding a next radio frame transmission format in a previous radio frame as in the third embodiment proposed above. . However, since a method that does not require such pre-signaling is also possible, the embodiment described below describes a method of transmitting and receiving control information regarding the transmission format without using the above-described pre-signaling.

In the first method according to the present embodiment, every radio frame, or a specific OFDM symbol of a specific radio frame, for example, the first OFDM symbol has the same cyclic prefix length and the remaining OFDM symbols are radio. It is a method of transmitting with a different cyclic prefix length according to a radio frame. At this time, the mobile terminal receives the first OFDM symbol of each radio frame after transmitting the information to distinguish the length of the cyclic prefix for the remaining OFDM symbols of the radio frame to the first OFDM symbol of each radio frame. The length of the cyclic prefix of the OFDM symbols can be known and correctly received. That is, when the mobile terminal does not know in advance the length of the cyclic prefix for any OFDM symbol transmitted in a specific radio frame, not only data demodulation but also control information included in the radio frame cannot be correctly demodulated. Therefore, the first OFDM symbol of the radio frame uses a cyclic prefix of a predetermined length to enable the mobile terminal to correctly receive the OFDM symbol. Also, the length of the cyclic prefix for the remaining OFDM symbols is the first OFDM symbol. It can be indicated by a variety of control information that can be transmitted through. As a result, the mobile station can correctly receive the first OFDM symbol of each radio frame because it is transmitted by a cyclic prefix of a predetermined length, and the remaining OFDM symbols are obtained through control information included in the first OFDM symbol. The information regarding the length of the cyclic prefix can be correctly received.

5 is a diagram illustrating an OFD symbol on which a synchronization channel is transmitted.

As a specific example of the above method, as shown in the example of FIG. 5, an OFDM symbol to which a synchronization channel (SCH) transmitted for downlink initial synchronization establishment is transmitted is a cyclic prefix of another OFDM symbol transmitted within the radio frame. Regardless of the length, it can be transmitted by a cyclic prefix of a predetermined length. In this way, the mobile terminal can establish a synchronization channel by searching for a synchronization channel and assuming a synchronization channel of the same format irrespective of which transmission format of the transmission frame. In addition, the control channel transmitted in an OFDM symbol such as the synchronization channel itself or the synchronization channel may include length information of the cyclic prefix used for the other OFDM symbols of the current radio frame.

The second method according to the present embodiment is a method for receiving by assuming that the mobile terminal has a shortest cyclic prefix length of a specific OFDM symbol. The mobile communication system may transmit an OFDM symbol included in the radio frame with a cyclic prefix of different lengths for each radio frame. However, the mobile station assumes and receives the shortest cyclic prefix length among the possible cyclic prefix lengths for the first OFDM symbol for the first OFDM symbol of each radio frame. In this case, the mobile terminal attempts to demodulate assuming that the OFDM symbol is transmitted with a shorter cyclic prefix, and in fact, even though the OFDM symbol is transmitted with a longer cyclic prefix, the mobile terminal has a OFDM transmission / reception structure. Correct demodulation is possible in. However, the reception error rate may be greater than when demodulating assuming the length of the actually transmitted cyclic prefix. If the length of the cyclic prefix is correctly assumed for the first OFDM symbol, the control information included in the OFDM symbol can be obtained to obtain the length of the cyclic prefix for the OFDM symbol transmitted thereafter. Therefore, correct reception is possible. If it is assumed that the length of the cyclic prefix is short, the mobile station fails to correctly receive the first OFDM symbol. The mobile terminal assumes the cyclic prefix of the largest length possible and tries demodulation of the first OFDM symbol again. In the present embodiment, it is preferable that data transmitted through the OFDM symbol is encoded by an encoding method capable of error detecting. The mobile terminal demodulates the OFDM symbol and then examines the demodulated data by the error detection code. The data that passes the test is treated as received correctly, and the data that does not pass the test is treated as not received correctly. The type of the error detection code is not limited, and a cyclic redundancy check (CRC) method may be used. In addition, it is preferable that the first OFDM symbol of each radio frame includes control information for distinguishing the length of the cyclic prefix of the remaining OFDM symbols. The control information about the length of the cyclic prefix for the remaining OFDM symbols may be information about the length of the cyclic prefix or information indicating the length of the cyclic prefix, and the mobile terminal may determine the length of the cyclic prefix. The length of the cyclic prefix for the remaining OFDM symbols can be obtained by receiving distinguishable control information, and the respective OFDM symbols can be correctly demodulated using the length of the cyclic prefix.

Those skilled in the art through the above description can be seen that various changes and modifications can be made without departing from the spirit of the present invention. Therefore, the technical scope of the present invention is limited to the contents described in the detailed description of the specification or by the claims.

In a cellular mobile communication system using OFDMA, multicast / broadcast data transmitted identically in a plurality of cells and unicast data transmitted to a specific terminal for each cell are transmitted together in a cellular mobile communication system using OFDMA. There is an effect of minimizing the required signaling and the waste of frequency-time resources.

Claims (33)

In the method for transmitting any data symbol by a plurality of subcarriers, Obtaining multicast / broadcast data and unicast data to transmit; Multiplexing the multicast / broadcast data and unicast data and transmitting them in units of radio frames including at least one data symbol; And And transmitting information about a transmission format indicating information about the property of the radio frame to a mobile terminal. A method of transmitting data using multiple subcarriers. The method of claim 1, wherein the transmitting step, The transmission of the multicast / broadcast data and the unicast data at different transmission times may be performed. A method for transmitting data using a plurality of subcarriers characterized in that. The method of claim 1, wherein the transmitting step, To transmit the frequency domains in which the multicast / broadcast data and the unicast data are transmitted differently. A method for transmitting data using a plurality of subcarriers characterized in that. The method of claim 1, wherein the transmitting step, Transmitting each of the multicast / broadcast data and unicast data through a specific frequency domain at a specific transmission time. A method for transmitting data using a plurality of subcarriers characterized in that. The method of claim 1, Transmitting, to the mobile terminal, indication information indicating that the transmitted radio frame is multiplexed with the multicast / broadcast data and unicast data. A method for transmitting data using a plurality of subcarriers, characterized in that it further comprises. The method of claim 5, The indication information includes any one of the information on the multiplexing method and the information on the amount of multicast / broadcast data transmitted. A method for transmitting data using a plurality of subcarriers characterized in that. The method of claim 5, The indication information is transmitted to the mobile terminal at a preset time. A method for transmitting data using a plurality of subcarriers characterized in that. The method of claim 5, The indication information is included in the radio frame to be transmitted A method for transmitting data using a plurality of subcarriers characterized in that. delete The method of claim 1, The information about the transmission format includes one of the number of data symbols included in the radio frame, the length of a cyclic prefix transmitted with the data symbol, and information about a pilot signal included in the radio frame. A method for transmitting data using a plurality of subcarriers, characterized in that. The method of claim 1, The information about the transmission format for the current radio frame is included in the radio frame before the current radio frame and transmitted. A method for transmitting data using a plurality of subcarriers characterized in that. The method of claim 1, The length of the cyclic prefix transmitted with the data symbol is variable A method for transmitting data using a plurality of subcarriers characterized in that. The method of claim 1, The length of the cyclic prefix transmitted with the first data symbol of the radio frame is fixed. A method for transmitting data using a plurality of subcarriers characterized in that. 14. The method of claim 13, Transmitting the information regarding the length of the cyclic prefix transmitted together with the remaining data symbols except for the first data symbol in the first data symbol. A method for transmitting data using a plurality of subcarriers, characterized in that it further comprises. In a data frame consisting of at least one data symbol, Including multicast / broadcast data and unicast data to be transmitted, wherein the multicast / broadcast data and unicast data are located in different frequency-time domains within the data frame, Each data is transmitted by the data symbol, and the data symbol is transmitted by a plurality of subcarriers. A data frame transmitted using a plurality of subcarriers characterized in that. delete delete delete 16. The method of claim 15, The pilot signal of a specific size corresponding to each of the data And a data frame transmitted using a plurality of subcarriers. In the method for receiving any data symbol transmitted by a plurality of subcarriers, Receiving a signal multiplexed with multicast / broadcast data and unicast data in units of radio frames including at least one data symbol; Obtaining the multicast / broadcast data and unicast data from the received signal; And Receiving information about a transmission format indicating information about an attribute of the radio frame; A method of receiving data using a plurality of subcarriers. The method of claim 20, wherein the receiving step, Receiving with different reception times for receiving the multicast / broadcast data and unicast data A method for receiving data using a plurality of subcarriers characterized in that. The method of claim 20, wherein the receiving step, Receiving by differentiating the frequency domain in which the multicast / broadcast data and unicast data are received A method for receiving data using a plurality of subcarriers characterized in that. The method of claim 20, wherein the receiving step, Receiving each of the multicast / broadcast data and unicast data through a specific frequency region at a specific reception time A method for receiving data using a plurality of subcarriers characterized in that. 21. The method of claim 20, Receiving indication information indicating that the multicast / broadcast data and unicast data are multiplexed in the radio frame; A method for receiving data using a plurality of subcarriers, characterized in that it further comprises. 25. The method of claim 24, The indication information includes any one of information on the multiplexing method and information on the amount of multicast / broadcast data transmitted. A method for receiving data using a plurality of subcarriers characterized in that. 25. The method of claim 24, The indication information is transmitted at a preset time A method for receiving data using a plurality of subcarriers characterized in that. 25. The method of claim 24, The indication information is included in the radio frame A method for receiving data using a plurality of subcarriers characterized in that. delete 21. The method of claim 20, The information about the transmission format includes one of the number of data symbols included in the radio frame, the length of a cyclic prefix transmitted with the data symbol, and information about a pilot signal included in the radio frame. A method for receiving data using a plurality of subcarriers, characterized in that. 21. The method of claim 20, The information about the transmission format for the current radio frame is included in the radio frame before the current radio frame and transmitted. A method for receiving data using a plurality of subcarriers characterized in that. 21. The method of claim 20, The length of the cyclic prefix transmitted with the data symbol is variable A method for receiving data using a plurality of subcarriers characterized in that. 21. The method of claim 20, The length of the cyclic prefix transmitted with the first data symbol of the radio frame is fixed. A method for receiving data using a plurality of subcarriers characterized in that. 33. The method of claim 32, Receiving information on the length of the cyclic prefix transmitted with the remaining data symbols except the first data symbol through the first data symbol The method for receiving data using a plurality of subcarriers, characterized in that it further comprises.

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