KR20050113366A - Apparatus and method for brodacasting service in a mobile communication by use of orthogonal freqeucny divisional multiple - Google Patents

Abstract

The present invention provides a mobile communication system including a plurality of base stations that provide a broadcast service to a mobile terminal, wherein the plurality of base stations are divided into at least two forms, and the divided base stations are configured by using predetermined orthogonal macro diversity. A method for transmitting a signal for a broadcast service to a mobile terminal, the method comprising: modulating a signal to be transmitted to the mobile terminal, partially encoding a modulation symbol to be transmitted in an orthogonal frequency division multiple symbol of the signal to be transmitted; And storing the partially coded symbols on the orthogonal frequency division multiple symbols so that they are carried on the same subcarrier, and transmitting the fastened Fourier transforms.

Description

Broadcasting service method and apparatus using orthogonal frequency multiplexing in mobile communication system {APPARATUS AND METHOD FOR BRODACASTING SERVICE IN A MOBILE COMMUNICATION BY USE OF ORTHOGONAL FREQEUCNY DIVISIONAL MULTIPLE}

The present invention relates to a method and apparatus for providing a broadcast service in a mobile communication system, and more particularly, to a method and apparatus for efficiently providing a broadcast service using diversity in a mobile communication system using an orthogonal frequency division multiplexing scheme. .

In general, a mobile communication system has been developed to provide a voice service, and a typical example of such a mobile communication system is a code division multiple access (CDMA) mobile communication system. The mobile communication system has evolved from providing only a voice service to a mobile communication system providing low-speed data. Since then, the mobile communication system has been developed into a system for providing only high-speed data and a high-speed data and voice service. Doing.

On the other hand, the mobile communication system has been evolving toward providing more various services as it can provide data services. For example, there are internet services, video services, and financial services. Various attempts have been made to provide a broadcast or multicast service to a mobile communication terminal. A mobile communication system in which such a broadcast service is provided will be described in detail.

A CDMA mobile communication system such as a typical cellular mobile communication system, for example, a high-speed data system, supports only a unicast service, not a broadcast service in which a plurality of mobile terminals receive the same data information. However, as communication technologies have evolved along with user demands, cellular mobile communication systems have evolved to support broadcast services in which a plurality of mobile terminals receive the same data information.

Next, a broadcast service provided to the high speed data (HRPD) cellular mobile communication system will be described with reference to the accompanying drawings. The cellular mobile communication system can support a broadcast service using an existing physical layer structure by appropriately changing the signaling.

1 is a diagram illustrating a structure of a transmission signal when supporting a forward broadcast service in a conventional HRPD cellular mobile communication system.

Referring to FIG. 1, a signal transmitted by a base station to a mobile terminal during one slot is composed of 2048 chips, and one chip has a transmission period of about 0.8 占 sec. In addition, one slot is divided into four traffic signal transmission sections, four medium access control (MAC) channel sections, and two burst pilot sections. During one slot, the spread signal is spread through the CDM scheme for a total of 1600 chips, and data for a broadcast service is transmitted to the mobile terminal in the traffic signal.

As shown in FIG. 1, when transmitting a spread spectrum traffic signal in a CDM scheme, the base station has a short PN having a base station-specific offset to a signal spread orthogonally with a Walsh code. (Pseudo Noise) Code is transmitted by complex multiplication. Here, complex multiplication is a method for minimizing the mutual interference effect that may be applied to each other when a plurality of base stations transmit different signals with the same Walsh code when transmitted in the CDM scheme.

The reception performance in the case of using the above method is limited by the number of wireless multipaths that the mobile terminal can recover. In general, since the receiver of this terminal of the CDM method is designed to recover 4 to 10 wireless multipaths, the wireless multipath of a part beyond the number of radio paths that can be restored can be restored. none. In the case of a broadcast service, since the same traffic signal is transmitted by a plurality of base stations, and the signals transmitted by other base stations have the same characteristics as those of the wireless multipaths with respect to each other, there may be a number of wireless multipaths that cannot be recovered by all mobile terminals. . In this case, the wireless multipath, which the mobile terminal cannot recover, may cause interference effects on the mobile terminal, thereby reducing the reception performance of the mobile terminal. An example of generating such an interference effect will be described with reference to the drawings.

FIG. 2 is a diagram illustrating a case where wireless multipaths, which cannot be restored by a mobile terminal according to the related art, cause interference effects to the mobile terminal.

Referring to FIG. 2, a mobile station (MS) 10 receives a broadcast service from a base station (BS A, B, C, D, E, F, G) 21 to 26. As a case, the mobile terminal 10 may restore only the radio multipath generated by the broadcast traffic signal transmitted by the base stations 21 and 24. In this case, the broadcast traffic signals transmitted by the remaining base stations 22, 23, 25, 26, 27 cause an interference effect on the mobile terminal, and the interference effect degrades the reception performance of the mobile terminal.

In order to solve this problem and transmit more data, orthogonal frequency multiplexing (hereinafter, abbreviated as OFDM) scheme has been used as a broadcast standard. A configuration of a transmission signal in the OFDM communication system is as shown in FIG. 3.

Referring to FIG. 3, the transmission signal is a signal transmitted in time by the physical layer. The configuration of the signal transmitted by the base station during the one slot to the mobile terminal is the same as that of FIG. 1, and the traffic signal spread by the OFDM scheme is transmitted during the interval corresponding to a total of 1600 chips during one slot. Data for the transmission is carried on the traffic signal to the mobile terminal.

When transmitting data for a broadcast service using the OFDM scheme, the mobile station can recover transmission signals from a plurality of base stations using a receiver structure whose complexity is independent of the number of wireless multipaths. When transmitting data for a broadcast service using the OFDM scheme, a case in which the mobile terminal can recover signals transmitted from a plurality of base stations will be described with reference to FIG. 4.

Referring to FIG. 4, when transmitting a transmission signal having a structure as shown in FIG. 3, a portion of a signal transmitted from each base station (Sector A to G) 31 to 37 using OFDM is transmitted to a mobile terminal. The same signal is received at different time intervals. That is, a portion of the plurality of base stations transmitted using the OFDM scheme is received by the mobile terminal receiver as a plurality of wireless multipaths, and the mobile station of the OFDM scheme converts the received signal using a fast Fourier transform regardless of the number of wireless multipaths. Can be restored using FFT).

As such, the broadcast service transmission signal transmitted using the OFDM scheme is received at the same time interval when the wireless multipaths of the signals transmitted from the plurality of base station transmitters are received by the mobile terminal, thereby improving performance due to macro diversity. Does not maximize. This case will be described in detail with reference to FIG. 5.

Referring to 5, base station A and base station B transmit data for the same broadcast service using an OFDM scheme. As shown in the graph 51, the signal transmitted from the base station A is received by the wireless channel in wireless multipaths having a time delay of 2 chips and 7 chips, respectively, to the mobile terminal receiver. As shown in the graph 52, the signal transmitted by the base station B is also received by the wireless channel in wireless multipaths having a time delay of 2 chips and 7 chips, respectively.

When data for the same broadcast service is transmitted by OFDM, as shown in the graph 53, multiple paths received in the same time interval are consequently combined to have the same characteristics as one radio path. That is, it has a 2-chip time delay, and has a radio path of base station A and a 2-chip time delay, and the received radio path of base station B is non-coherent in the mobile terminal receiver. ) Has the same characteristics as one wireless multipath. Here, the non-coherent summation has a 2-chip time delay and the radio path of the received base station A and the 2-chip time delay and the received radio path of the base station B are combined without correction for the phase change caused by the radio channel. General characteristics of OFDM.

However, the OFDM cannot separate the multipaths by separately combining the multipaths in a signal having a plurality of multipaths and do not combine them, and must simultaneously correct the signals having a plurality of multipaths mixed. Therefore, the OFDM-based mobile communication system cannot coherently merge signals from other transmitters received in the same time interval. As a result, as shown in FIG. 5, the mobile station receives a signal for a broadcast service from two different base stations, but the diversity that can be obtained does not differ from when receiving from one base station.

Accordingly, an object of the present invention is to provide a method and apparatus for providing an efficient broadcast service in a mobile communication system.

Another object of the present invention is to provide a method and apparatus for providing a broadcast service using frequency or time orthogonal macro diversity to maximize diversity in an OFDM communication system.

The method for achieving the above object of the present invention, in a mobile communication system including a plurality of base stations for providing a broadcast service to a mobile terminal, the plurality of base stations are divided into at least two forms, the predetermined base station A method for transmitting a signal for a broadcast service to the mobile terminal using orthogonal macro diversity, the method comprising: modulating a signal to be transmitted to the mobile terminal and a modulation symbol to be transmitted in an orthogonal frequency division multiple symbol of the signal to be transmitted And storing the partial coded symbols so that they are carried on the same subcarrier in the orthogonal frequency division multiple symbol, and transmitting the transformed symbols by fast Fourier transform.

 The apparatus for achieving the object of the present invention, in a mobile communication system including a plurality of base stations for providing a broadcast service to a mobile terminal, the plurality of base stations are divided into at least two forms, the predetermined base station An apparatus for transmitting a signal for a broadcast service to the mobile terminal using orthogonal macro diversity, the modulator for modulating a signal to be transmitted to the mobile terminal, and a transmission interval of consecutive orthogonal frequency division multiple symbols of the signal to be transmitted. A partial coder that partially encodes a modulation symbol to be transmitted to each of two consecutive symbols, and a modulation symbol buffer to store the two coded symbols to be carried on the same subcarrier of a transmission interval of the orthogonal frequency division multiplexed symbols different from each other And inverse fast Fourier transform the stored symbols. And a reverse fast Fourier transformer for transmitting.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The present invention to be described below will be described by applying an OFDM mobile cellular communication system. In addition, a space time block code or a frequency before transmitting a signal transmitted by the base stations constituting the cellular mobile communication system supporting the broadcast service by the OFDM scheme in a manner of maximizing macro diversity A method of transmitting a signal after encoding using a space frequency block code will be described. In the method of increasing diversity using the time interval block code or the frequency interval block code, a signal encoded with the time interval block code or the frequency interval block code is generally transmitted using a plurality of transmitting antennas. This method requires a plurality of antennas for each base station. Instead of using the plurality of antennas, the present invention divides the base stations distributed in the mobile communication system into two or more types (for example, Type A and Type B), and then divides them. A signal is transmitted by using two transmission antennas.

When the base stations of the mobile communication system are divided into two types as described above, as shown in FIG. 6, two types of base stations are mixed in one mobile communication system. The two types of base stations properly transmit signals encoded with a time interval block code or a frequency interval block code.

Next, a structure of a signal transmitted for a broadcast service in a mobile communication system using an OFDM scheme will be described. In order to maximize macro diversity for efficient broadcasting service, frequency orthogonal macro diversity or time orthogonal macro diversity may be used. First, a signal structure in the case of transmitting a signal using orthogonal macro diversity will be described in detail with reference to the accompanying drawings.

7 is a diagram illustrating a signal structure when a signal is transmitted using a frequency orthogonal macrodiversity sheet in an OFDM mobile communication system according to a preferred embodiment of the present invention. 7 is an example of applying a space frequency block code to a signal in a frequency domain.

Referring to FIG. 7, as illustrated in FIG. 3, a signal transmitted by a base station to a mobile terminal during one slot is composed of 2048 chips. Has a transmission period of about 0.8 μsec. In addition, one slot is divided into four traffic signal transmission sections, four medium access control (MAC) channel sections, and two burst pilot sections.

The traffic signal transmission interval is 400 chips, and the OFDM symbol (s _{i, 0} , ..., s _{i, N-1} or -s ^* _{i, of the} A type base station (TYPE A) or B type base station (TYPE B) _{, 1} , s ^* _{i, 0,} …, -s ^* _{i, N-1} , s ^* _{i, N-2} ), that is, data for a broadcast service is transmitted. The transmitted symbol is then FOMDed. Here, FOMD (Frequency Orthogonal Macro Diversity) processing means that a signal that is properly encoded and encoded by a Space Frequency Block Code according to which type of A type base station or B type base station is appropriately arranged and transmitted in the frequency domain.

The modulation symbol transmitted on each subcarrier of the OFDM symbol is encoded with a frequency interval block code together with the modulation symbol of an adjacent subcarrier and then transmitted. That is, in FIG. 7, the 2nth modulation symbol to be transmitted in the i th OFDM symbol is encoded with a frequency interval block code together with the 2n + 1th modulation symbol. The frequency interval block code encodes the 2n th coded symbols s _{i, 2n} and the 2n + 1 th coded symbols s _{i, 2n + 1} output from the modulator, and is a result of encoding the s _{i, 2n} and s _{i in} the A-type base station. _{, 2n + 1} on a continuous subcarrier to transmit. Then, the type B base station transmits -s ^* _{i, 2n + 1} and s ^* _{i, 2n} , which are the result of the encoding _, on a continuous subcarrier. s ^* _{i, 2n} and s _{i, 2n} have a conjugate relationship with each other.

The signal encoded in FIG. 7 is transmitted on a continuous subcarrier and is transmitted on a continuous subcarrier when the frequency interval block code is applied. It can be minimized.

When transmitting in this manner, even if the multi-paths of the received signal of the A type base station and the male signal of the B type base station overlap in the same time interval, the mobile terminal can separate and coherently combine the corresponding signals using the frequency interval block code. have. When multipaths overlap, when the signals transmitted from different base stations can be separated and coherently combined, the mobile station can obtain diversity to increase reception performance.

Next, an example of transmitting a signal by maximizing macro diversity using a time interval block code will be described. .

8 is a diagram illustrating a signal structure when a signal is transmitted using a time-orthogonal macrodiversity sheet in an OFDM mobile communication system according to a preferred embodiment of the present invention.

Referring to FIG. 8, a signal transmitted by a type A base station and a type B base station to a mobile terminal during one slot consists of 2048 chips, and one chip has a transmission period of about 0.8 μsec. In addition, one slot is divided into four traffic signal transmission sections, four medium access control (MAC) channel sections, and two burst pilot sections.

The traffic signal transmission interval consists of 400 chips. In the A type base station (TYPE A), (s _{i, 0} , s _{i + 1,0} , s _{i, 2} ,.., S _{i, N-2} , s _{i + 1, N-2} ) are _stored in the i th OFDM symbol. (S _{i, 1} , s _{i + 1,1} , s _{i, 3} ,…, s _{i, N-1} , s _{i + 1, N-1} ) in the i + 1th OFDM symbol It is carried on the traffic signal transmission interval. In the B-type base station (TYPE B), the i-th OFDM symbol (-s ^* _{i, 1} , -s ^* _{i + 1,1} , -s ^* _{i, 3} , … , -s ^* _{i, N-1} , -s ^* _{i + 1, N-1} ) with (-s ^* _{i, 0} , -s ^* _{i + 1,0} , -s ^* _{i, 2} , … , -s ^* _{i, N-2} , -s ^* _{i + 1, N-2} ) are transmitted on the traffic signal transmission interval with a silier time difference. That is, data for broadcast service is transmitted. The transmitted symbol is then FOMDed. Here, the FOMD processing means that a signal that is properly encoded and encoded by a time interval code according to which type of A type base station or B type base station is appropriately disposed in the frequency domain and transmitted.

In FIG. 8, the 2nth modulation symbol to be transmitted in the ith OFDM symbol is encoded with a time interval block code along with a 2n + 1th modulation symbol. The time interval block code encodes 2n-th modulation symbols s _{i, 2n} and 2n + 1-th modulation symbols s _{i, 2n + 1} output from the modulator, and is encoded by the A-type base station s _{i, 2n} , s _{i. And 2n + 1} are transmitted on an m th subcarrier of an i th OFDM symbol and an m th subcarrier of an i + 1 th OFDM symbol, respectively. Also, in the B-type base station, -s ^* _{i, 2n + 1} , s ^* _{, which is a} result of time interval block code encoding on the 2nth modulation symbols s _{i, 2n} and 2n + 1th modulation symbols s _{i, 2n + 1} output from the modulator. _{i and 2n} are respectively transmitted on the m th subcarrier of the i th OFDM symbol and the m th subcarrier of the i + 1 th OFDM symbol. The transmission of the time interval block code encoding result using the same mth subcarrier in the i th OFDM symbol and the i + 1 th OFDM symbol is performed through the same fading as much as possible. Interference can be minimized by breaking orthogonality.

As shown in FIG. 7, the method of transmitting on a continuous subcarrier using a frequency interval block code may degrade performance when a maximum delay spread of a wireless channel is large. In this case, even if the continuous subcarriers may take different fading, the orthogonality of the frequency block code may be destroyed. As shown in FIG. 8, the method of transmitting a continuous subcarrier using a frequency block block code may have a deterioration in performance due to a loss of orthogonality of the frequency block block code when the maximum delay spread is large. However, the speed of the mobile terminal does not affect the orthogonality of the frequency block code.

On the other hand, when the result coded using the time interval block code is transmitted on the same carrier of consecutive OFDM symbols as shown in FIG. 8, the orthogonality of the time interval block code is related to the maximum delay spread of the radio channel. It doesn't matter. Instead, if the speed of the mobile terminal is too high, the fading of time-contiguous OFDM symbols may be different, thereby destroying the orthogonality of the time interval block code.

In the case of applying the frequency section block code as shown in FIG. 7 and the time section block code as shown in FIG. 8, the method of transmitting as shown in FIG. 7 has a maximum delay. This is suitable when the spread is not large and the speed of the mobile terminal is large. On the other hand, the method of transmitting as shown in FIG. 8 is suitable when the maximum delay spread is large while the speed of the mobile terminal is relatively large. Therefore, as shown in FIG. 7, the cellular mobile communication system supporting the broadcasting service broadcasts to any type of mobile terminal in a wireless environment, whether to transmit by applying a frequency interval block code or a transmission by applying a time interval block code. It may be determined by whether to transmit a signal.

7 and 8 illustrate a structure of a transmission signal for a case in which only one of frequency orthogonal macro diversity and time orthogonal macro diversity is supported, but as shown in FIG. Diversity and temporal orthogonal macro diversity can be mixed in the same slot. Accordingly, the diversity gain performance of the frequency interval block code applied to the frequency domain and the time interval block code applied to the time domain can be partially obtained.

As shown in FIG. 9, when a frequency orthogonal macrodiversity and a time orthogonal macrodiversity are mixed and transmitted in one signal, OFDM transmitted in the same time interval as the first base station of type A base station and the type B base station Only one of frequency orthogonal macro diversity and time orthogonal macro diversity may be applied to a symbol. That is, other methods cannot be applied to the i-th OFDM symbol, such as frequency orthogonal macro diversity in the A type base station and time orthogonal macro diversity in the B type base station.

A structure of a base station transmitter of a mobile communication system in the case of using time orthogonal macro diversity among the diversity as described above will be described with reference to the accompanying drawings.

10 is a diagram illustrating a structure of a base station transmitter for transmitting broadcast data using time orthogonal macro diversity in a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 10, broadcast data to be transmitted as a broadcast signal is channel encoded by the channel encoder 110, and the channel encoded result is input to the channel interleaver 120 and interleaved. The channel interleaved signal is input to the repeating / puncturing unit 130. Here, the repeater / puncture unit 130 determines the coded symbols to be transmitted through puncturing or repetition when the number of coded symbols output from the channel interleaver 120 is larger or smaller than the number of coded symbols that can be transmitted.

The repeated or punctured signal is input to the modulator 140. The modulator 140 then modulates the input signal in the same manner as QPSK or 16QAM and transmits the modulated result to the orthogonal macro diversity transmission processor 150.

The orthogonal macro diversity transmission processor 150 uses time orthogonal macro diversity and is input to a time orthogonal macro diversity signal generator (not shown) and encoded using a time interval block code. That is, as shown in FIG. 8, when OFDM symbols s (2n) and s (2n + 1) are transmitted, s (2n) and s (2n + 1) are output from an A-type base station. The second base station outputs -s ^* (2n + 1), s ^* (2n).

The signal encoded using the time interval block code as described above is input to the modulation symbol buffer 160. Then, the modulation symbol buffer 160 collects modulation symbols transmitted in two OFDM symbols in the case of temporal orthogonal macro diversity and arranges them appropriately in the wave region. That is, a transmission signal of an OFDM symbol is generated. The transmission signal of the OFDM symbol generated as described above is input to the serial / parallel converter 170, serial / parallel transform, and then to the Inverse Fast Fourier Transform (IFFT) 180.

The inverse fast Fourier transformer 180 inverts the input OFDM symbol by inverse fast Fourier transform and outputs a signal in a time domain. Then, the cyclic prefix inserter 190 inserts the CP into the signal in the time domain and transmits the CP to the mobile terminal.

A structure of an apparatus for generating a temporal orthogonal macro diversity signal for generating a temporal orthogonal macro diversity signal in first and second base station transmitters having such a structure will be described in detail with reference to the accompanying drawings.

11 is a diagram illustrating a structure of an apparatus for generating a temporal orthogonal macro diversity signal in an A-type base station transmitter according to an embodiment of the present invention.

Referring to FIG. 11, modulation symbols to be transmitted to two OFDM symbols input from the modulator 140 (s _{i, 0} , s _{i, 0} .... s _{i + 1, N-2} , s _{i + 1, N-1} are partially coded by a time interval block code by two consecutive modulation symbols in the partial encoder 151. Here, partial encoding is performed using an Alamouti code. The partial coded result is stored in a modulation symbol buffer 160 capable of storing 2N modulation symbols such that two coded symbols output from one partial coder are carried on the same subcarrier of different OFDM symbols. Coded symbols input to the modulation symbol buffer 160 are s _{i, 0} , s _{i, 0} .... s _{i -} th OFDM symbol in inverse fast Fourier transformer 180 after the partial coding and storage of the modulation symbols of s _{i + 1, N-2} and s _{i + 1, N-1} are completed Inverse fast Fourier transform (IFFT) for i, and inverse fast Fourier transform (IFFT) for i + 1 th OFDM symbol are processed and then transmitted.

12 is a diagram illustrating a structure of an apparatus for generating a temporal orthogonal macro diversity signal in a type B base station transmitter according to an embodiment of the present invention.

Referring to FIG. 12, modulation symbols s _{i, 0} , to be transmitted to two OFDM symbols input from the modulator 140. s _{i, 0} .... s _{i + 1, N-2} , s _{i + 1, N-1} are partially encoded by a time interval block code by two modulation symbols consecutively by the partial encoder 151 (Partial). Alamouti Encode). The partial coded result is input to and stored in a modulation symbol buffer 160 capable of storing 2N modulation symbols such that two coded symbols output from one subcoder are carried on the same subcarrier of different OFDM symbols. Coded symbols input to the modulation symbol buffer 160 are s _{i, 0} , s _{i, 0} .... s _{i + 1, N-2} , s _{i + 1, N-1 After} the partial coding and storage of the modulation symbols are all completed, the i th OFDM symbol in the inverse fast Fourier transformer 180 Inverse Fast Fourier Transform (IFFT) for i) and Inverse Fast Fourier Transform (IFFT) for i + 1 th OFDM symbol are divided and processed before being transmitted.

As described above, a transmitter for generating a time orthogonal macro diversity signal has been described with reference to FIGS. 10, 11, and 12, and a transmitter structure for generating a frequency orthogonal macro diversity signal is similarly applied to the structure described above. Can be. However, when generating a frequency orthogonal macro diversity signal, an apparatus for generating a time orthogonal macro diversity signal as shown in FIGS. 11 and 12 should be changed and applied as shown in FIGS. 13 and 14, respectively.

Meanwhile, a structure of a mobile terminal receiver of a mobile communication system in the case of using time orthogonal macro diversity among the diversity as described above will be described with reference to the accompanying drawings.

FIG. 15 illustrates a structure of a broadcast signal receiver of a mobile terminal for transmitting broadcast data using time orthogonal macro diversity in a mobile communication system according to an embodiment of the present invention.

Referring to FIG. 15, the mobile terminal receiver outputs a signal in a frequency domain by performing fast Fourier transform on a fast Fourier transformer (FFT) 210 for the received OFDM symbol. This is then performed via the bottle / serial converter 220 and then stored in the modulation symbol buffer 230. The modulation symbol buffer 230 stores modulation symbols input from two OFDM symbols.

Thereafter, the orthogonal macro diversity reception processor 240 receives a modulation symbol from the modulation symbol buffer 230 and inputs it to a time orthogonal diversity signal detector (not shown) included therein. The signal detector then decodes the time interval block code and simultaneously estimates and corrects the fading channel. The signal detected in the form of a modulation symbol in the orthogonal macro diversity reception processor 240 is input to the demodulator 250 and demodulated, and then repeated with respect to the coded symbol output from the combining and zero insertion unit 260. Join the parts and insert a '0' for the perforated parts. The combined and '0' inserted signals in the combiner 260 are stored in the code symbol buffer 270. Here, the combiner 260 is a device necessary to receive and decode all transmitted coded symbols when symbols encoded for one encoder packet are transmitted in a plurality of OFDM symbols.

The coded symbols in which the coded symbols of one coded packet are stored in the code symbol buffer 270 are deinterleaved in the channel interleaver 280 and then input to the channel decoder 290 and decoded.

7 to 9 show signals for the result of applying only one of time orthogonal macro diversity or frequency orthogonal macro diversity in one OFDM symbol. Such time orthogonal macro diversity or frequency orthogonal macro diversity may be mixed in one OFDM symbol, and may also be mixed with a non-broadcast unicast signal to which time orthogonal macro diversity is not applied.

FIG. 16 is a diagram illustrating a state in which a unicast signal to which neither time nor frequency orthogonal macro diversity is applied is mixed in one OFDM symbol according to the second embodiment of the present invention.

In FIG. 16, a signal having time orthogonal macro diversity is transmitted over two OFDM symbols, while a signal having frequency orthogonal macro diversity is transmitted over only one OFDM symbol. In this case, when the time or frequency orthogonal macro diversity is used, the mobile terminal receiver should be able to separately estimate the fading channel from the A-type base stations and the paging channel from the base station B base stations. As such a method of channel estimation separately, the pilot signal transmitted from the A-type base stations and the pilot signal transmitted from the B-type base stations should be designed such that they do not interfere with each other by having orthogonality with each other.

FIG. 17 is a diagram illustrating an example of a method of transmitting a pilot signal transmitted from a base station when using time orthogonal macro diversity or frequency orthogonal macro diversity according to embodiments of the present invention.

When using the time orthogonal macro diversity or the frequency orthogonal macro diversity, the mobile terminal should be able to independently estimate the fading channels from type A and type B base stations. To this end, type A and type B base stations separately allocate a location in a frequency domain in which pilot subcarriers are to be transmitted. That is, the A-type base station carries a pilot subcarrier on the fifth, eleventh, seventeenth, and twenty-third subcarriers, as shown in FIG. On the other hand, the B-type base station carries pilot subcarriers on the 6th, 12th, 18th, and 24th subcarriers and transmits them. When transmitting a pilot subcarrier in this manner, the A-type base station should not transmit any signal to the 6th, 12th, 18th, and 24th subcarriers, and likewise, the second base station transmits the 5th, 11th, 17th, and 23rd. No signal shall be transmitted on the subcarrier. If this is not observed, the pilot subcarriers transmitted from the A-type base station and the B-type base station are interfered by signals of each other and smooth channel estimation is impossible.

FIG. 18 is a diagram illustrating another example of a method of transmitting a pilot signal transmitted from a base station when using a time or frequency orthogonal macro diversity sheet according to embodiments of the present invention.

Referring to FIG. 18, the A-type base station and the B-type base station allocate the same positions in the frequency domain for transmitting the pilot subcarriers, and set the A-type base station and the B-type base station to transmit the pilot subcarriers at different times. . Accordingly, interference with pilot subcarriers can be prevented. That is, in FIG. 18, the A-type base station carries pilot subcarriers on 5th, 10th, 15th, and 20th subcarriers of an even (2n) OFDM symbol. On the other hand, the B-type base station carries a pilot subcarrier on the same subcarrier position of an odd numbered (2n + 1) OFDM symbol and transmits it. In the even-numbered OFDM symbol, only the A-type base station transmits a pilot subcarrier. In the odd-numbered OFDM symbols, only the Type B base station transmits pilot subcarriers, but both the first and second base stations may transmit pilot subcarriers within the same OFDM symbol.

FIG. 19 is a diagram illustrating another example of a pilot signal transmission method transmitted from a base station when using an inter- or frequency-orthogonal macro diversity sheet according to an embodiment of the present invention.

Referring to 19, a type A base station transmits pilot subcarriers to fifth and tenth subcarriers in an even (2n) OFDM symbol. In contrast, the B-type base station transmits pilot subcarriers to the 15th and 20th subcarriers in an even (2n) OFDM symbol.

In addition, the first base station transmits pilot subcarriers to the 15th and 20th subcarriers in odd-numbered (2n + 1) OFDM symbols, and the B-type base station transmits to the fifth and 10th subcarriers in odd-numbered (2n + 1) OFDM symbols. Transmit pilot subcarriers. Even when the pilot subcarriers are transmitted in this manner, the pilots at the first and second base stations may be received by the mobile terminal without interference with each other.

Briefly describing the transmission schemes of the pilot signals as described above, the first transmission scheme as shown in FIG. 17 is orthogonality by separating the pilot signals transmitted by the A-type base stations and the B-type base stations in the frequency domain. It is a way to have. The second transmission scheme as shown in FIG. 18 is a scheme that has orthogonality by separating pilot signals transmitted from the A-type base station and the B-type base station in the time domain. In addition, the third transmission method as shown in FIG. 19 is a method of having orthogonality by separating pilot signals transmitted from the A-type base station and the B-type base station in time and frequency domains. In addition to the orthogonality using the frequency and time domains, other methods may be applicable in which pilot signals transmitted by the A-type base station and the B-type base station are orthogonal to each other.

In the broadcasting system using time orthogonal macro diversity or frequency orthogonal macro diversity as described above, when the mobile station knows whether a specific base station is an A type base station or a B type base station, the mobile station may improve performance by using such information. In this case, when the performance can be improved by determining whether a specific base station is a type A base station or a type B base station, the strengths of signals received from the type A base station or the type B base station are not equal, and one side is significantly stronger than the other. It's time to be weak. As such, when the strength of signals received from A-type base stations or B-type base stations is unbalanced, attempting to recover broadcast information using a signal transmitted from a base station having a relatively low reception power is a signal band of the received signal. This can have the effect of increasing the noise ratio. For example, when the strength of the signal received from the type A base station is 20 dB stronger than the signal received from the type B base station, there is little effect of increasing the signal-to-noise ratio of the broadcast information signal using the signal from the type B base station. On the other hand, in this case, the noise increases considerably, which may result in a lower signal-to-noise ratio.

One way for a mobile terminal to know whether a particular base station is a type A base station or a type B base station may be performed in a time orthogonal macro diversity or frequency orthogonal macro diversity scheme transmitted as shown in FIGS. 7 and 8. It is a method of associating a type A or B type with a short PN code offset of a corresponding base station.

As shown in FIG. 7 or 8, in the mobile communication system according to the present embodiment, a total of 512 different Sort PN code offsets are possible, and each Sort PN code offset is separated by at least 64 chips from each other. It is. In order to associate a specific base station with A type or B type with a short PN code offset of the base station, the following Equation 1 is applied when the base station is A type, and in the case of B type, the following Equation 2> apply the method.

As described above, when the Sort PN code offset of the corresponding base station to transmit the broadcast signal in the time orthogonal macro diversity or frequency orthogonal macro diversity scheme is a multiple of 128, the type B base station is set to a type A base station. The base station makes an appointment with the mobile terminal. In addition to the same method as in Equation 1 and Equation 2, it is possible to associate the short PN code offset of the base station with either A type or B type and apply the same. have.

Using a method of associating the Sort PN code offset of the base station with either A type or B type, the mobile station receives a neighbor list from the base station and sorts the Sort PN code of the base stations in the vicinity of the base station. After identifying the offset, it is used to classify the base stations of type A and base stations of type B and compare the received power received from each type of base station to broadcast the received signals of base stations of type A and base stations of type B. Decide whether to use them together to restore or to use only one of them. That is, when the ratio of the signal strength received from the base stations of the A type and the base stations of the B type exceeds a certain value, the broadcast information is restored by using only the received signal for one of the two types. In both cases, the broadcast information is restored using both.

The time orthogonal macro diversity or frequency orthogonal macro diversity scheme as described above may be adopted as an optional feature in a mobile communication system and a mandatory requirement in a mobile terminal when it is adopted in a mobile communication standard supporting a broadcast service. . That is, the base station transmits a signal for a broadcast service using a time orthogonal macro diversity or a frequency orthogonal macro diversity scheme in a mobile communication system or using only one of a type A base station and a type B base station. Can be. In this case, the base station uses a signaling to inform the mobile terminal whether to use a time orthogonal macro diversity or a frequency orthogonal macro diversity scheme, and if the scheme is not used, a transmission scheme and a B form of the A-type base station. Notifies the mobile terminal of information about which of the base station transmission methods is transmitted. Accordingly, the mobile terminal can simplify the reception process and at the same time improve the reception performance.

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 the equivalents of the claims.

As described above, the present invention applies a time orthogonal macro diversity or frequency orthogonal macrodiversity scheme in an OFDM mobile communication system and divides into a specific A type and B type base station and transmits a broadcast signal to a mobile terminal for more efficient broadcasting service. It can be performed, there is an effect that can improve the reception performance of the mobile terminal.

1 is a diagram illustrating a structure of a transmission signal when supporting a forward broadcasting service in an HRPD cellular mobile communication system according to the related art;

2 is a diagram illustrating a case in which wireless multipaths that cannot be restored by a mobile terminal according to the related art cause interference effects to the mobile terminal.

3 is a diagram illustrating a structure of a transmission signal in an OFDM mobile communication system according to the prior art;

4 is a diagram illustrating a case in which a mobile terminal can recover signals transmitted from a plurality of base stations when transmitting data for a broadcast service using an FDM scheme according to the prior art;

FIG. 5 is a diagram illustrating a case in which a macrodiversity sheet is not obtained as much as possible when transmitting the same broadcast data in a plurality of base stations using the OFDM scheme according to the prior art; FIG.

6 is a view showing a state in which two types of base stations are mixed in a mobile communication system according to an embodiment of the present invention;

7 is a diagram illustrating a signal structure when a signal is transmitted using a frequency orthogonal macrodiversity sheet in an OFDM mobile communication system according to an embodiment of the present invention;

8 is a diagram illustrating a signal structure when a signal is transmitted using a time-orthogonal macrodiversity sheet in an OFDM mobile communication system according to an embodiment of the present invention;

FIG. 9 is a diagram illustrating a signal structure when a frequency orthogonal macro diversity and a time orthogonal macro diversity are mixed and transmitted in one signal according to a preferred embodiment of the present invention. FIG.

10 illustrates a structure of a base station transmitter for transmitting broadcast data using time orthogonal macro diversity in a mobile communication system according to an embodiment of the present invention;

11 is a diagram illustrating a structure of an apparatus for generating a temporal orthogonal macro diversity signal in an A-type base station transmitter according to an embodiment of the present invention;

12 illustrates a structure of an apparatus for generating a temporal orthogonal macro diversity signal in a type B base station transmitter according to an embodiment of the present invention;

13 and 14 illustrate structures of an apparatus for generating a frequency orthogonal macro diversity signal in a type A base station and a type B base station transmitter according to an embodiment of the present invention;

15 illustrates a structure of a broadcast signal receiver of a mobile terminal for transmitting broadcast data using time orthogonal macro diversity in a mobile communication system according to an embodiment of the present invention;

FIG. 16 illustrates a state in which a unicast signal to which neither time nor frequency orthogonal macro diversity is applied is mixed in one OFDM symbol according to the second embodiment of the present invention;

17 is a diagram illustrating an example of a pilot signal transmission scheme transmitted from a base station of a mobile station when using time orthogonal macro diversity or frequency orthogonal macro diversity according to embodiments of the present invention;

18 is a diagram illustrating another example of a transmission method of a pilot signal transmitted from a base station when using a time or frequency orthogonal macro diversity sheet according to embodiments of the present invention;

19 is a view showing another example of a transmission method of a pilot signal transmitted from a base station when using an inter or frequency orthogonal macrodiversity sheet according to an embodiment of the present invention.

Claims (8)

In a mobile communication system including a plurality of base stations for providing a broadcast service to a mobile terminal, the plurality of base stations are divided into at least two forms, and the separated base stations broadcast to the mobile terminal using a predetermined orthogonal macro diversity. In the method for transmitting a signal for a service, Modulating a signal to be transmitted to the mobile terminal; Partially encoding a modulation symbol to be transmitted in an orthogonal frequency division multiple symbol of the transmission signal; Storing the partially coded symbols to be carried on the same subcarrier in the orthogonal frequency division multiple symbol; And performing a fast Fourier transform on the stored symbols. The method of claim 1, In the partial encoding process, when the predetermined orthogonal macro diversity is time orthogonal macro diversity, the modulation symbols to be transmitted in the consecutive orthogonal frequency division multiplex symbols by using two consecutive time interval block codes Said method of partial coding. The method of claim 2, The storing may include storing the partially coded symbols on the same subcarrier in a transmission interval of the orthogonal frequency division multiplex symbols different from each other. The method of claim 1, The partial encoding may include performing partial encoding on one modulation symbol to be transmitted in the orthogonal frequency division multiple symbol by using a frequency interval block code when the predetermined orthogonal macro diversity is frequency orthogonal macro diversity. Way. In a mobile communication system including a plurality of base stations for providing a broadcast service to a mobile terminal, the plurality of base stations are divided into at least two forms, and the separated base stations broadcast to the mobile terminal using a predetermined orthogonal macro diversity. An apparatus for transmitting a signal for a service, the apparatus comprising: A modulator for modulating a signal to be transmitted to the mobile terminal; A partial encoder for partially encoding a modulation symbol to be transmitted in two consecutive symbols in a transmission interval of the continuous orthogonal frequency division multiple symbol of the transmitted signal; A modulation symbol buffer for storing the partially coded two coded symbols to be carried on the same subcarrier in a transmission interval of the orthogonal frequency division multiple symbol which is different from each other; And an inverse fast Fourier transformer for transmitting the stored symbols by inverse fast Fourier transform. The method of claim 5, The partial coder partially encodes modulation symbols to be transmitted in the consecutive orthogonal frequency division multiple symbols when the predetermined orthogonal macro diversity is time orthogonal macro diversity using a time interval block code of two consecutive symbols. The device, characterized in that. The method of claim 6, The modulation symbol buffer stores the partially coded symbols so that the partially coded symbols are carried on the same subcarrier in a transmission interval of the orthogonal frequency division multiplex symbols different from each other. The method of claim 5, Wherein the partial encoder partially encodes one modulation symbol to be transmitted in the orthogonal frequency division multiple symbol by using a frequency interval block code when the predetermined orthogonal macro diversity is frequency orthogonal macro diversity.