KR20080041543A - Apparatus for cooperative diversity in mobile station of down link using relay station of ofdma system - Google Patents

Abstract

An apparatus for cooperative diversity in a downlink MS by using an OFDMA(Orthogonal Frequency Division Multiple Access) system based RS is provided to transmit signals to the same time/frequency resource areas at the same time, thereby improving receiving performance through diversity effects. A BS(Base Station)(300-1) transmits a downlink signal. An RS(Relay Station)(310-1) transmits the downlink signal from the BS to an MS(Mobile Station)(330). The MS receives the downlink signal which is transmitted from the BS and the RS and has increased receiving power by multiple signal sources, and provides the received downlink signal to a user. The BS and the RSs transmit the same signal to the MS in an assigned time-frequency resource area.

Description

Apparatus for cooperative diversity in mobile station of down link using relay station of OFDMA system}

1 is a view configured to enable communication in a network expansion or high quality using a relay station in the prior art.

2A and 2B are examples of a transmission structure between a base station and a relay station using different time or frequency resources in the configuration of FIG. 1, respectively.

3A to 3C illustrate an example of configuring cooperative signal source diversity using a relay station according to the present invention.

4A to 4D illustrate an example of configuring a cooperative transmission diver seat using a relay station according to the present invention.

5A and 5B illustrate an example of configuring cooperative complex diversity using a relay station according to the present invention.

6A to 6D illustrate an example of a structure for transmitting a signal for cooperative diversity using a relay station in a 2-hop network.

7A to 7B show an example of a structure for transmitting a signal for cooperative diversity using a relay station in a multi-hop network of three-hop networks.

8 is a graph comparing BER performance by cooperative signal source diversity according to the present invention.

9 compares BER performance with cooperative transmission diversity according to the present invention.

The present invention relates to a communication network, and to an OFDMA based communication network composed of a base station and a mobile station.

In particular, the present invention provides a downlink (DL) link in an OFDMA (orthogonal frequency division multiple access) based communication network including a base station (BS) and a mobile station (MS). In case that BS transmission signal is difficult to communicate with MS or in shadow area or low quality area, relay station (RS) is used to enable network expansion or high quality communication.

1 is a view configured to enable communication in a network expansion or high quality using a relay station in the prior art. In a conventional OFDMA-based communication network composed of a BS and an MS, a BS transmission signal of a downlink (DL) is difficult to communicate to the MS, or a communication area can be communicated in a shaded area or a low quality area as illustrated in FIG. 1. Use to configure network expansion or high quality communication.

2A and 2B are examples of a transmission structure between a base station and a relay station using different time or frequency resources in the configuration of FIG. 1, respectively.

The transmission structure between the BS 100 and the RS 110 is BS-RS transmission using different time or frequency resources as shown in FIG. 2B illustrating the transmission structure in the same frame and delay transmission structure in units of frames in FIG. 2A. Avoid collision between the interval and the RS-MS transmission interval.

The purpose of RS in IEEE 802.16j is to expand the communication area and increase the amount of transmission. Therefore, because the signal of BS-RS section and the signal of RS-MS section can be different, communication is impossible due to mutual interference when using the same resource. to be.

In the conventional RS-based communication network, since the MS performs reception and demodulation using only RS transmission signals, there is a limitation in reception performance. In the RS-MS transmission interval, the BS cannot use resources in this area. There is a problem of an idle region section and a resource.

The technical problem to be achieved by the present invention, to solve the above problems, downlink using an OFDMA system-based relay station that can improve the reception performance by the diversity effect by simultaneously transmitting a signal in the same time / frequency resource region The present invention provides a cooperative diversity apparatus at a terminal.

In accordance with an aspect of the present invention, there is provided a cooperative diversity apparatus in a downlink terminal using an OFDMA system-based relay station, including: a base station transmitting a downlink signal; A relay station for transmitting a downlink signal from the base station to a mobile station; And a mobile station transmitted from the base station and the relay station to receive and provide a downlink signal having an increased reception power due to multiple signal sources to the user.

At this time, the base station and the relay station transmits the same signal to the mobile station in the allocated time-frequency resource region, or the plurality of relay stations exist, so that each of the plurality of relay stations transmit the same signal in the allocated time-frequency resource region. Or a plurality of relay stations exist so that the base station and each of the plurality of relay stations transmit the same signal to the mobile station in the allocated time-frequency resource region.

The base station or one or more relay stations simultaneously transmits different space-time encoded signals to the mobile station in the time-frequency resource region retransmitted through the relay station.

The base station transmits different space-time encoded signals generated by performing space-time encoding to the relay station and the mobile station, respectively, and the relay station retransmits the received signal to the mobile station, or the base station transmits the original signal to the relay station. And the original signal is space-time encoded and transmitted to the mobile station, and the relay station is space-time encoded by the base station and transmitted to the mobile station, or the relay station exists in plural, and the base station transmits different signals space-time encoded. Each of the plurality of relay stations, wherein the plurality of relay stations retransmits signals from the base station to the mobile station, or the plurality of relay stations exist, and the base station transmits original signals to the plurality of relay stations, Each relay station is responsible for the transmitted signal Different space-time encoding is performed to retransmit the space-time encoded signal to the mobile station.

Alternatively, in the time-frequency resource region retransmitted through the relay station, base stations or multiple relay stations are grouped by space-time codes so that the signal sources in the group transmit the same space-time coded signals, and different space-time coded signals for each group.

In this case, a plurality of relay stations exist, and each relay station performs time-space encoding of signals transmitted from the base station to transmit different space-time encoded signals to the mobile station, and the base station is space-time transmitted from any one of the base stations. The same space-time coded signal as the coded signal is transmitted to the mobile station in the same time-frequency domain, or the base station transmits a space-time coded signal, and each relay station is different from the base station, and each relay station receives the same space-time coded signal. Transmit to the base station in the same time-frequency domain.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Composition of the Invention

The present invention relates to cooperative source diversity (CSD), in which multiple signal sources simultaneously transmit the same signal to the same resource, and cooperative transmission diversity in which multiple signal sources simultaneously transmit heterogeneous signals by space-time encoding. Cooperative Transmit Diversity (CTD), or Cooperative Hybrid Diversity (CHD) using a combination of the above two methods.

CSD is a method of obtaining a diversity effect by transmitting the same signal for the same time-frequency resources in a single or multiple RSs as well as a BS, and is configured as shown in FIGS. 3A to 3C to obtain a gain.

3a shows a signal s ₁ (t) at a BS 300-1 having the same value as a time-frequency resource allocated for an MS in a two-hop network and a signal s ₀ (t) at a MS 310-1. The case of simultaneous transmission to 330 is shown.

Figure 3b that illustrates a case in which multiple signals transmitted at the same time the RS for a signal transmitted from the BS (300-2) in a multi-hopmang the MS (330), 2 multiplets RS of RS ₀ (310- as a configuration example 2) and s ₀ (t), s ₁ (t) with the same value from multiple RSs 310-2, 320-2 to MS 330 as the time-frequency resources allocated for RS ₁ 320-2. ) Shows that the signal is transmitted.

FIG. 3C illustrates a case in which a signal transmitted from the BS 300-3 is simultaneously transmitted as multiple RS signals to the MS 330 in a multihop network. As a configuration example, the signal s ₁ from the BS 300-3 is illustrated. (t), transmission signal s ₀ (t) from RS ₀ 310-3, which is one of the multiple RSs for two multiple RSs, and transmission signal s ₂ (t) from the remaining RS ₁ 320-3 Is transmitted, transmitting the same value with the same time-frequency resources allocated to obtain diversity gain.

3a to 3c, signals received between the BS and the RS corresponding to some of the entire time-frequency resources transmitted from the BS are demodulated by the RS and transmitted as they are, or the modulation order is changed or the channel code is changed. When RS-MS transmission is performed by modifying the signal, the BS simultaneously transmits the same signal type for the same time-frequency resource region. At this time, in the receiver MS, the added noise layer is constant, but the reception power of the signal is increased by multiple signal sources, thereby improving reception performance.

At this time, even if a transmission time difference occurs between multiple signal sources, if the time difference is within the Cyclic prefix interval in the OFDMA system, the MS is compensated by the OFDMA channel estimation function, so that a diversity effect can be obtained without any problem even when a transmission time difference occurs. do.

3A, 3B, and 3C described above illustrate a case in which there is a frame-by-frame delay in transmission by relaying from the RS to the original BS data. CSD applies equally.

CTD is a method of obtaining transmit diversity by transmitting different signals through different space-time encoding to each signal source for the same time / frequency resource in a single or multiple RSs as well as a BS, and may be configured as shown in FIGS. 4A to 4D. have.

FIG. 4a illustrates a case where all space-time encoding is performed on a transmission path in a BS in a two-hop network, and FIG. 4b illustrates a case in which space-time encoding is performed separately by a transmission path in a BS and an RS in a two-hop network. FIG. 4c illustrates a case where all spatiotemporal coding for all transmission paths is performed in a BS in a multihop network, and FIG. 4d illustrates a case where spatiotemporal coding for each transmission path is performed separately in multiple RSs in a multihop network.

In FIG. 4A, BS 400-1 performs space-time encoding with (S _{i +1} , S ^* _i ) and (S _i , -S ^* _{i + 1} ), and RS (410-1) with (S _i , -S ^* _{i + 1} ) transmits the space-time encoded signal to the MS 430 (S _{i +1} , S ^* _i ). In addition, the RS 410-1 relays the received (S _i , -S ^* _{i + 1} ) signal back to the MS 430, and transmits (S _{i +} ) to the same time-frequency resource in the MS 430. Diversity is obtained by simultaneously receiving a space-time encoded signal with ₁ , S ^* _i ) and (S _i , -S ^* _{i + 1} ).

In this case, in order to obtain transmit diversity with different space-time codes with the same time-frequency resource at the receiving MS 430, the relay in RS 410-1 may transmit in the same frame as shown in FIG. 6A and a frame as shown in FIG. 6B. It consists of delayed transmission. Both methods use a method of transmitting different space-time coded signals in the same area in the BS 400-1 for the time-frequency domain relayed in the RS 410-1.

FIG. 4B shows different space-time encoding for the same time-frequency domain in transmission from BS 400-2 and RS 410-2 to MS 430, respectively (S _{i +1} , S ^* _i ). And (S _i , -S ^* _{i + 1} ) signals are transmitted to the MS 430 to obtain transmit diversity.

The BS-RS transmission signal is transmitted to RS 410-2 as an original data signal that is not space-time encoded, and is space-time encoded from RS 410-2 to (S _i , -S ^* _{i + 1} ) to MS 430. In this case, the BS 400-2 also transmits a signal encoded by another space-time code (S _{i +1} , S ^* _i ) to the same time-frequency domain. The space-time encoding performed by the BS 400-2 and the RS 410-2 may be divided into any _one of (S _{i + 1} , S ^* _i ) and (S _i , -S ^* _{i + 1} ). .

FIG. 4C shows a multiple relay RSs 420-3 and 410-3 by performing space-time encoding with (S _{i +1} , S ^* _i ) and (S _i , -S ^* _{i + 1} ) in BS 400-3. ) Separates each space-time coded signal (S _{i +1} , S ^* _i ) and (Si, -S ^* _{i + 1} ) and transmits them respectively, and receives multiple RSs (420-3, 410-3) The same space-time encoded signal is transmitted to the MS 430 so that the MS 430 obtains transmit diversity.

FIG. 4D illustrates a configuration for performing each space-time encoding in multiple RSs. In the BS 400-4, the original data signals S _i and S _{i +1} are multiple RSs 410-4 and 420-4. ), And the multiple RSs 410-4 and 420-4 perform different space-time encoding, respectively, and in RS ₀ 410-4, the space-time encoded signals of (S _i , -S ^* _{i + 1} ) RS ₁ 420-4 transmits the (S _{i +1} , S ^* _i ) space-time encoded signal to the MS 430 in the same time-frequency resource region to obtain transmit diversity. In this case, the space-time coding in the multiple RSs 410-4 and 420-4 may be divided into any of (S _{i +1} , S ^* _i ) and (S _i , -S ^* _{i + 1} ).

That is, in FIGS. 4A to 4D, a signal transmitted between BSs-RSs corresponding to a part of total time-frequency resources transmitted from a BS is transmitted through a space-time encoding process at a certain RS and another at another RS or BS. By simultaneously transmitting through a space-time encoding process, a transmission diversity gain is obtained in a MS using multiple RS or BS transmission signals. In this case, the MS must support transmit diversity, and the BS operates in a different mode that performs all or part of space-time encoding or transmits unencoded original data, unlike conventional transmit diversity.

In addition, in FIG. 4, classification is performed according to a position at which space-time encoding is performed. A method of performing all spatio-temporal coding in the BS centrally (FIGS. 4A and 4C) and a method of dividing different spatio-temporal coding according to signal sources (FIGS. 4B and 4D) are possible. In order for the constructed encoding to be performed separately, a space-time encoder needs to be built in the RS.

CHD is a mixture of the two diversity schemes mentioned above, and the space-time code, which is widely used in transmit diversity, is limited to a signal source. In the case of the Alamouti technique applied to two transmission paths, when applied to the cooperative diversity of the present invention, the cooperative diversity is configured by dividing into two groups and transmitting the same space-time encoded signal for each group. can do. Diversity effect by CSD is obtained in channel estimation through the same space-time coded transmission signals, and the received signal having SNR increased by CSD is obtained by CTD diversity effect by space-time decoding. 5A and 5B show a case where two transmitting antenna based Alamouti techniques are applied to CHD using RS.

In FIG. 5A, multiple RSs 510-1 and 520-1 apply CTD, and transmission signals from each of the RSs 510-1 and 520-1 are different from each other. For example, the transmission signals of some RSs are shown in FIG. 5B, and the transmission signals of the multiple RSs 510-2 and 520-2 are the same for the CSD, and the BS 500-2 is the same. In the CTD, the transmission signal is different from the transmission signal in the multiple RSs 510-2 and 520-2.

In FIG. 5A, the transmission signals from the multiple RSs 520-1 and 510-1 to the MS 530 in charge of relaying are (S _{i +1} , S ^* _i ) and (S _i , -S ^* _{i + 1} ), respectively. Different space-time encoded signals are transmitted to form a CTD, and when the BS 500-1 transmits a signal from the multiple RSs 510-1 and 520-1 to the MS 530, the multiple RSs 510-1 and 520- The same space-time coded signal as that of some RS of the transmission signal of 1) is transmitted. At this time, the BS 500-1 transmits the same space-time coded signal as the RS ₀ 510-1 to the MS 530 in the same time-frequency domain to configure the CSD in the MS 530.

5B is similar in configuration to that of FIG. 5A, but the multiple RSs 510-2 and 520-2 transmit the same space-time coded signals to the same time-frequency domain to configure a CSD at the receiving end of the MS 530. The BS 500-2 transmits a space-time encoded signal different from the transmission signals of the multiple RSs 510-2 and 520-2 to the MS 530 simultaneously in the same time-frequency domain to obtain a CTD. will be.

As a signal transmission structure for CSD, CTD, and CHD, a signal transmission structure for cooperative diversity using RS in a 2-hop network is shown in FIGS. 6A to 6D, and a signal for cooperative diversity using RS in a multihop network is shown in FIGS. The transmission structure is shown in Figs. 7A and 7B as an example of three hops.

In the transmission structure, the same time / frequency resource is configured to be transmitted from multiple signal sources at the same time, and according to the type of signal transmitted simultaneously, the diversity effect by the CSD, CTD, or the CHD fused with two methods is obtained.

Description of operation of the invention

CSD is simply relayed or reprocessed at RS for data transmitted to BS-RS, and when signal is transmitted to MS, multi-signal at MS by simultaneously transmitting same signal at BS or multiple RS in multi-hop network over 2 hops Receive the original signal.

The CTD transmits one space-time coded signal from the RS to data transmitted to the BS-RS, and transmits another space-time coded signal from a signal source such as BS or another RS simultaneously in the same time-frequency resource region. In an MS that supports diversity, multiple space-time coded multiple signal sources are received to obtain a gain due to transmit diversity.

The CHD is divided into groups that transmit the same spatiotemporal coded signal for the same time / frequency resource for the BS and multiple RSs to obtain the diversity effect by the CSD in the group and the CTD between the coded groups. Can be.

The above three cooperative diversity schemes are performed in the transmission schemes of FIGS. 6 and 7 to obtain diversity effects in the target MS reception.

FIG. 6A illustrates a transmission structure in the same frame when the RS transmission signal and the BS transmission signal are used in reception of an MS, and when the relayed RS-MS signal is transmitted, the same signal is simultaneously transmitted from the BS to the same time-frequency domain. A method of transmitting the present invention is applied to the case of FIGS. 3A, 4A, and 4B.

FIG. 6B illustrates a frame delay transmission structure using an RS transmission signal and a BS transmission signal. Unlike FIG. 6A, when the RS-MS signal relayed with a frame-by-frame delay is transmitted, the same time-frequency domain is used in the BS. A method of transmitting the same signal at the same time as in FIG. 3A, 4A and 4B is applied.

FIG. 6C illustrates a case where only multiple RS transmission signals are used for reception of an MS, and when only signals of multiple RSs are used for an MS as shown in FIGS. 3B, 4C, and 4D, when transmitting from multiple RSs to an MS, FIG. It consists of the same signal or different coded signal transmissions for the same time-frequency domain.

FIG. 6D illustrates a transmission structure when a BS signal is simultaneously used in the same time-frequency domain simultaneously with the multiple RS transmission signals. In FIG. 3C, FIG. 5A, and FIG. 5B, FIG. Applies when used together.

FIG. 7A illustrates a transmission structure using multiple RS transmission signals in case of a multihop network, in which a first hop is BS-RS ₀ , a second hop is RS ₀ -RS ₁ , and a last hop is RS ₁ Illustrated as a 3-hop network with -MS. This is a structure in which RS ₀ is simultaneously transmitted to the MS even in RS ₀ in the same time-frequency domain when RS ₁ -MS is transmitted at the reception of the target MS. The reception of the target MS is the same as the case of using multiple RS signals, and in the configuration of FIGS. 3B, 4C, and 4D, the cooperative diversity for the RS-MS interval is extended to multiple hops.

FIG. 7B illustrates a transmission structure extended to multiple hops when multiple RS transmission signals and BS signals are used at a receiving end of an MS. Although extended to multiple hops through RS ₀ and RS ₁ to the target MS, the MS reception uses both multiple RS signals and BS signals, and multiple RS and BS signals are applied to the target MS in FIGS. 3C, 5A, and 5B. When used together, it applies to multiple hops.

FIG. 8 shows BER performance when the CSD, CTD, and CHD are applied at the same output for the signal source for the 2-hop BS-RS-MS transmission.

Since the CSD has multiple signal sources, the added noise layer is constant but the power of the signal source is increased, thereby obtaining the diversity gain. In the MS, no additional function is required for this, and the channel estimation function of the existing OFDMA modem also solves the time difference problem of several signal sources. Simulation results show that there is a 3dB improvement in performance when both signals of BS and RS are used as compared to BS-RS-MS as a single signal source at BER = 10-5. Such a simulation will be apparent to those of ordinary skill in the art to which the present invention pertains.

When the CTD is received by applying space-time coding to multiple signal sources individually, the CTD obtains the same transmit diversity effect as that of the multiple transmit antenna system, thereby improving reception performance. FIG. 8 shows simulation results of Alalouti, which is a typical transmission diversity scheme, for two types of signals. As shown in FIG. 8, the signal is transmitted to BS-RS-MS as a single signal source at BER = 10-5. It can be seen that there is a 7dB performance improvement. Likewise, the description of such a simulation will be apparent to those skilled in the art, and thus a detailed description thereof will be omitted.

 Since CHD has a limited number of space-time codes applied to multiple signal sources, grouping of the same space-time coded signals enables diversity between CSD and CTD between groups to achieve two diversity effects. In the case of FIG. 5, the simulation is performed on three kinds of signal sources in FIG. 8, and as a result, when the signal is transmitted to the BS-RS-MS as a single signal source at BER = 10-5, 7.7 to It can be seen that there is a 9dB performance improvement.

FIG. 9 shows a simulation result using Alalouti, which is a typical transmission diversity scheme, for the two signal sources. As a result, there is an improvement of about 13 dB compared with the BS-MS transmission at BER = 10-5. It can be seen that there is a performance improvement of 10dB over the case of a single signal source transmitted to BS-RS-MS.

As a result, the present invention improves the reception performance by the diversity effect by simultaneously transmitting signals in the same time / frequency resource region. In the BS-RS-MS network structure, the BS simultaneously transmits the same resources in the BS in the RS-MS transmission interval. In the multi-hop multi-hop network structure, the BS-multi RS-MS network structure can obtain diversity gain by transmitting or mixing the same signal or space-time coded signal using the same resource simultaneously in not only BS but also multiple RSs. To provide an advantage. That is, the added noise layer is constant, but the power of the signal source is increased, thereby obtaining the diversity gain.

Those skilled in the art will appreciate that the present invention can be implemented in a modified form without departing from the essential features of the present invention. Therefore, the disclosed embodiments should be considered in descriptive sense only and not for purposes of limitation. Examples included in the above description are introduced for the understanding of the present invention, and these examples do not limit the spirit and scope of the present invention. It will be apparent to those skilled in the art that various embodiments in accordance with the present invention in addition to the above examples are possible. The scope of the present invention is shown not in the above description but in the claims, and all differences within the scope will be construed as being included in the present invention.

In addition, it can be easily understood by those skilled in the art that each of the above steps according to the present invention can be variously implemented in software or hardware using a general programming technique.

And some steps of the invention may also be embodied as computer readable code on a computer readable recording medium. The computer-readable recording medium includes all kinds of recording devices in which data that can be read by a computer system is stored. Examples of computer-readable recording media include ROM, RAM, CD-ROM, CD-RW, magnetic tape, floppy disks, HDDs, optical disks, magneto-optical storage devices, and carrier wave (eg, Internet It also includes the implementation in the form of). The computer readable recording medium can also be distributed over network coupled computer systems so that the computer readable code is stored and executed in a distributed fashion.

According to the present invention, an OFDMA system downlink diversity apparatus includes: a base station transmitting a downlink signal, a relay station transmitting a downlink signal from the base station to a mobile station, and an increase due to multiple signal sources transmitted from the base station and the relay station. Including a mobile station that receives and provides a downlink signal having a received reception power to a user, the added noise layer is constant, but the power of the signal source is increased, thereby providing a diversity gain.

The mobile station does not need additional functions to apply the present invention, and the time difference problem of various signal sources is solved together by the channel estimation function of the existing OFDMA modem. When the CTD is received by applying space-time coding to multiple signal sources individually, the CTD obtains the same transmit diversity effect as that of the multiple transmit antenna system, thereby improving reception performance. Since CHD has a limited type of space-time code applied to multiple signal sources, it is possible to obtain both diversity effects by applying the diversity effect by CSD and CTD between groups through grouping the same space-time coded signals. By providing a function, the quality of service provided to a user in mobile communication can be easily improved.

Claims (6)

A diversity apparatus for downlink in an OFDMA system, A base station transmitting a downlink signal; A relay station for transmitting a downlink signal from the base station to a mobile station; And A mobile station transmitted from the base station and the relay station to receive and provide a downlink signal having an increased reception power due to multiple signal sources to a user; and cooperative with the downlink terminal using an OFDMA system-based relay station. Diversity Device. The method of claim 1, The base station and the relay station transmits the same signal to the mobile station in the allocated time-frequency resource region, The plurality of relay stations exist such that each of the plurality of relay stations transmits the same signal to the mobile station in the allocated time-frequency resource region, or Cooperative diversity in a downlink terminal using an OFDMA system-based relay station, characterized in that there are a plurality of relay stations, so that the base station and each of the plurality of relay stations transmit the same signal to the mobile station in the allocated time-frequency resource region. Device. The method of claim 1, In a downlink terminal using an OFDMA system-based relay station, the base station or one or multiple relay stations simultaneously transmits different space-time coded signals for each signal source to the mobile station in a time-frequency resource region retransmitted through the relay station. Cooperative diversity device. The method according to claim 1 or 3, The base station transmits different space-time encoded signals generated by performing space-time encoding to the relay station and the mobile station, respectively, and the relay station retransmits the received signal to the mobile station, The base station transmits the original signal to the relay station and transmits the original signal to the mobile station by space-time encoding, and the relay station transmits the signal transmitted from the base station to the mobile station by space-time encoding, The relay station is provided in plural, the base station transmits a time-space encoded different signal to each of the plurality of relay stations, the plurality of relay stations retransmit the signal from the base station to the mobile station, or The plurality of relay stations exist, the base station transmits the original signal to each of the plurality of relay stations, and each relay station performs different space-time encoding on the transmitted signal to retransmit the space-time encoded signal to the mobile station. Cooperative diversity apparatus in a downlink terminal using an OFDMA system-based relay station. The method of claim 1, In the time-frequency resource region retransmitted through the relay station, base stations or multiple relay stations are grouped by space-time codes so that signal sources in the group transmit the same space-time coded signals, and groups transmit different space-time coded signals. Cooperative diversity apparatus in a downlink terminal using an OFDMA system-based relay station. The method according to claim 1 or 5, There are a plurality of relay stations, Each relay station performs space-time encoding of signals transmitted from the base station to transmit different space-time encoded signals to the mobile station, and the base station receives the same space-time encoded signals as those transmitted from any one of the base stations. To the mobile station in the same time-frequency domain, or The base station transmits a space-time coded signal, and each of the relay stations is different from the base station, and each relay station transmits the same space-time coded signal to the base station in the same time-frequency domain. Cooperative diversity device at the terminal.

Images