Integrated circuit

Abstract

A wireless communication system enabling multihop communication while maintaining the system throughput and preventing degradation of the user throughput. In the system, a BS (base station) determines the relaying method (whether an RS performs reproduction relay or nonreproduction relay) of the RS (relaying station) and the MCS of multihop communication according to the reception quality (the line quality among an MS2, the RS, and the BS) of the pilot for nonreproduction relay, the reception quality (the line quality between the RS and the BS) of the pilot 2 for reproduction relay, and the line quality (the line quality between the MS2 and the RS) measured at the RS. The determination result is transmitted as relay information to the RS and to the MS2 (a mobile station (2)) through the RS. The MS2 encodes and modulates the uplink data with the MCS based on the relay information and transmits the data to the RS. The RS relays the uplink data while selecting nonreproduction relay or reproduction relay according to the relay information.

Description

kids kinds of channel quality, so that, compared to conventional multi-hop communication where relay is always performed using only one relay scheme of either regenerative relay or non-regenerative relay, user throughput can be improved.

The configuration of the relay station (RS) according to this Embodiment will be described below. FIG. 10 illustrates the configuration of the RS.

In RS200 as shown in FIG. 10, the relay information (information indicative of the combination of the relay scheme and MCS), pilot signals (regenerative relay pilot 1 and non-regenerative relay pilot) and uplink data received in antenna 201 are subjected to radio processing such as down-conversion and the like in RF receiving section 202. In addition, the relay information is received from the BS, and the pilot signals and uplink data are received from the MS2. After the radio processing, the pilot signals are inputted to pilot decision section 203, and the relay information and uplink data are inputted to switching section 205.

Based on the flags added to the pilot signals, decision section 203 determines whether the pilot is regenerative relay pilot 1 or non-regenerative pilot, and inputs regenerative relay pilot 1 to received quality measuring section 204, while inputting non-regenerative relay pilot to amplifying section 206.

Received quality measuring section 204 measures the received quality of regenerative relay pilot 1, and obtains the MS2-RS channel quality. Then, the channel quality information indicating the obtained channel quality is inputted to coding section 209.

Switching section 205 has a table (part of the table of FIG. 6) indicative of the relationships between relay information and relay schemes/MCS, and, according to input relay information, selects a combination of the relay scheme and MCS and switches regenerative relay and non-regenerative relay. For example, referring to the table of FIG. 6, when relay information is “1”, the RS relays data by non-regenerative relay, and QPSK is used both in MS2-RS and RS-BS. Accordingly, when relay information is “1”, since the RS relays data by non-regenerative relay, uplink data is inputted to amplifying section 206. Meanwhile, for example, when relay information is “4”, since the RS relays data by regenerative relay, and 16QAM is used in MS2-RS while QPSK is used in RS-BS, uplink data is inputted to demodulation section 207. Further, switching section 205 inputs information about the selected MCS to demodulation section 207, decoding section 208, coding section 209 and modulation section 210.

Amplifying section 206 amplifies the uplink data and non-regenerative relay pilot to inputted to RF transmitting section 211.

Meanwhile, the uplink data inputted to demodulation section 207 is demodulated in demodulation section 207 and decoded in decoding 208 according to the MCS of MS2-RS designated by switching section 205. The result is encoded again in coding section 209 and modulated again in modulation section 210 according to the MCS of RS-BS designated by switching section 205. The modulated uplink data is inputted to RF transmitting section 211.

Meanwhile, channel quality information and regenerative relay pilot 2 are encoded in coding section 209, modulated in modulation section 210, and then inputted to RF transmitting section 211.

The uplink data (to be relayed in regenerative relay) inputted from modulation section 210 and the uplink data (to be relayed in non-regenerative relay) inputted from amplifying section 206 are subjected to radio processing such as up-conversion in RF transmitting section 211 and then transmitted to the BS via antenna 201. Further, channel quality information, regenerative relay pilot 2 and non-regenerative relay pilot are also subjected to radio processing such as up-conversion in RF transmitting section 211, and then transmitted to the BS via antenna 201. In addition, the relay information is transmitted to the MS2 in the relay scheme for the downlink data switched in the same way as uplink data.

As shown in FIG. 11, with the above-described BS and RS, when a MS2 newly joins in while communication is in progress between a MS1 and a BS via a RS by regenerative relay, multi-hop communication is made possible for the MS2 using the combination (non-regenerative relay/QPSK in FIG. 11) of a relay scheme and MCS capable of obtaining optimal transmission rates according to three kinds of channel quality, MS2-RS, RS-BS and MS2-RS-BS channel quality. Thus, by performing a relay capable of obtaining optimal transmission rates to the MS2, it is possible to maintain system throughput even when the MS2 newly joins in. Further, in particular, when non-regenerative relay is performed with the MS2, since the processing delay of non-regenerative relay is less than that of regenerative relay, communication occasions for the MS1 increase compared to the case of performing regenerative relay with the MS2, so that it is possible to prevent user throughput of the MS1 from decreasing. Furthermore, by decreases in the processing delay due to application of non-regenerative relay to the MS2, the system throughput can be increased.

In addition, when multiplexing schemes such as code division multiplex (CDM) and space division multiplex (SDM) are used in communications between the MS and RS, it is also possible to use the table shown in FIG. 12 instead of the table in FIG. 6.

In the table shown in FIG. 12, non-regenerative relay is adopted only when the RS-BS channel quality in regenerative relay is the same as the MS-RS-BS channel quality in non-regenerative relay. By using such a table, when the RS-BS channel quality is better than the MS-RS channel quality when regenerative relay is employed, it is possible to make the transmission rate between the RS and BS better than the transmission rate between the MS and the RS. Accordingly, as shown in FIG. 13, it is possible to multiplex the data of MS1-RS and the data of MS2-RS and transmit, and, as a result, it is possible to reduce the resources used between the RS and the BS. Further, by reducing the resources used between the RS and the BS, resources that can be used by another MS (MS3) connecting with the BS increase, and it is thus possible to further improve system throughput.

Further, when the MS2 is present in the service area of the BS, it is also possible to use a table as shown in FIG. 14, instead of the table of FIG. 6.

In the table shown in FIG. 14, in addition to the channel quality (MS2-RS channel quality and RS-BS channel quality) in regenerative relay and the channel quality (MS-RS-BS channel quality) in non-regenerative relay, channel quality (MS2-BS channel quality) in the case of direct connection between the MS2 and the BS without using the RS is also notified to the BS, and, from these kinds of channel quality, the BS determines one of direct connection, regenerative relay and non-regenerative relay to perform between the MS2 and B2 and MCS. In addition, in the case of direct connection, relay information is set for “0” irrespective of the MCS. By using such a table, when the channel quality is poor in communications via the RS, by directly connecting between the MS2 and the BS, it is possible to further improve system throughput.

Claims

1. A wireless communication system, comprising:

a mobile station;

a base station; and

a relay station, wherein the mobile station and the base station communicate via the relay station, wherein:

the relay station is configured for both a first relay scheme of a non-regenerative relay for amplifying a signal without changing a modulation scheme and performing a relay transmission, and a second relay scheme of a regenerative relay for changing the modulation scheme of the signal according to a channel quality and performing the relay transmission, and the relay station switches between the first and second relay schemes based on a combination of a first channel quality in the non-regenerative relay and a second channel quality in the regenerative relay.

2. The wireless communication system according to claim 1, wherein the base station comprises a table providing a relationship between the combination of the first channel quality in the non-regenerative relay and the second channel quality in the regenerative relay and the first and second relay schemes, and determines a relay scheme to be employed, with reference to the table.

3. The wireless communication system according to claim 2, wherein the base station transmits relay information indicating the determined relay scheme to the relay station.

4. The wireless communication system according to claim 1, wherein the relay station transmits a pilot signal for employment in a channel quality measurement to the base station in the non-regenerative relay, measures a channel quality between the mobile station and the relay station from the pilot signal as the second channel quality in the regenerative relay, and transmits a new pilot signal for employment in the channel quality measurement to the base station.

5. The wireless communication system according to claim 4, wherein the relay station transmits information indicating the measured channel quality to the base station.

6. The wireless communication system according to claim 1, wherein, when the regenerative relay is employed, the relay station determines a modulation scheme for a communication between the mobile station and the relay station.

7. A relay station apparatus switching between two relay schemes of a non-regenerative relay for amplifying a signal from a mobile station apparatus without changing a modulation scheme and performing a relay transmission, and a regenerative relay for changing the modulation scheme of the signal from the mobile station apparatus according to a channel quality and performing the relay transmission, the relay station apparatus comprising:

an amplifying section that amplifies the signal from the mobile station apparatus;

a demodulation section that demodulates the signal from the mobile station apparatus;

a modulation section that modulates the signal demodulated by the demodulation section using a modulation scheme in accordance with the channel quality;

a transmission section that transmits the signal amplified by the amplifying section or the signal modulated by the modulation section; and

a switching section that switches between the two relay schemes based on a combination of a first channel quality in the non-regenerative relay and a second channel quality in the regenerative relay, and outputs an input signal to the amplifying section when the non-regenerative relay is employed and outputs the input signal to the demodulation section when the regenerative relay is employed.

8. The relay station apparatus according to claim 7, further comprising:

a receiving section that receives a pilot signal for employment in channel quality measurement from the mobile station apparatus; and

a measuring section that measures a channel quality between the mobile station apparatus and the relay station apparatus from the pilot signal as the second channel quality in the regenerative relay.

9. The relay station apparatus according to claim 8, wherein the transmission section transmits the pilot signal to the base station in the non-regenerative relay and transmits a new pilot signal for employment in the channel quality measurement to the base station apparatus.

10. The relay station apparatus according to claim 8, wherein the transmission section further transmits information indicating the measured channel quality to the base station apparatus.

11. The relay station apparatus according to claim 7, wherein, when the regenerative relay is employed, the switching section determines a modulation scheme for a communication between the mobile station apparatus and the relay station apparatus.

12. The relay station apparatus according to claim 7, further comprising a receiving section that receives relay information indicating a relay scheme determined based on a relationship between the combination of the first channel quality in the non-regenerative relay and the second channel quality in the regenerative relay and the two relay schemes, and

wherein the switching section switches between the two relay schemes according to the relay information.

13. The relay station apparatus according to claim 12, further comprising a table providing a relationship between the relay information and the two relay schemes, and

wherein the switching section switches between the two relay schemes with reference to the table.

14. A wireless communication system, comprising:

a mobile station;

a base station; and

a relay station, wherein the mobile station and the base station communicate via the relay station,

wherein:

the relay station switches between two relay schemes of a non-regenerative relay for amplifying a signal without changing a modulation scheme and performing a relay transmission, and a regenerative relay for changing the modulation scheme of the signal according to a channel quality and performing a relay transmission, based on a combination of a first channel quality in the non-regenerative relay and a second channel quality in the regenerative relay; and

the base station comprises a table providing a relationship between the combination of the first channel quality in the non-regenerative relay and the second channel quality in the regenerative relay and the two relay schemes, and determines a relay scheme to be employed, with reference to the table.

15. The wireless communication system according to claim 14, wherein the base station transmits relay information indicating the determined relay scheme to the relay station.

16. An integrated circuit configured to control a relay station apparatus to select from two relay schemes of a non-regenerative relay for amplifying a signal transmitted from a transmission apparatus without regenerating the signal with a decoding-reencoding process and performing a relay transmission of the amplified signal, and a regenerative relay for regenerating a signal transmitted from the transmission apparatus with a decoding-reencoding process and performing a relay transmission of the regenerated signal, the integrated circuit comprising:

an amplifying section configured to control amplification of the signal transmitted from the transmission apparatus when the non-regenerative relay is employed;

a decoding section configured to control decoding of the signal transmitted from the transmission apparatus when the regenerative relay is employed;

an encoding section configured to control reencoding of the signal decoded by the decoding section to generate a regenerated signal; and

a transmission section configured to control transmission of the amplified signal or the regenerated signal depending on a combination of a first channel quality in the non-regenerative relay and a second channel quality in the regenerative relay.

17. The integrated circuit according to claim 16, further comprising:

a reception section configured to control reception of a pilot signal for employment in channel quality measurement from the transmission apparatus; and

a measuring section configured to control measurement of a channel quality between the transmission apparatus and the relay station apparatus from the pilot signal as the second channel quality in the regenerative relay.

18. The integrated circuit according to claim 17, wherein the transmission section transmits the pilot signal to a reception apparatus in the non-regenerative relay and transmits a new pilot signal for employment in the channel quality measurement to the reception apparatus.

19. The integrated circuit according to claim 17, wherein the transmission section further transmits information indicating the measured channel quality to a reception apparatus.

20. The integrated circuit according to claim 16, wherein, when the regenerative relay is employed, a modulation scheme for a communication between the transmission apparatus and the relay station apparatus is determined.

21. The integrated circuit according to claim 16, further comprising a reception section configured to control reception of relay information indicating a relay scheme determined based on a relationship between the combination of the first channel quality in the non-regenerative relay and the second channel quality in the regenerative relay and the two relay schemes,

wherein one of the two relay schemes is selected according to the relay information.

22. The integrated circuit according to claim 21, further comprising a table providing a relationship between the relay information and the two relay schemes,

wherein one of the two relay schemes is selected with reference to the table.

23. An integrated circuit configured to control a base station apparatus to communicate with a mobile station apparatus via a relay station apparatus, the integrated circuit comprising:

a receiving section configured to control reception of a first pilot signal for employment in a first channel quality measurement between the mobile station apparatus and the base station apparatus in a non-regenerative relay, and reception of a second pilot signal for employment in a second channel quality measurement between the relay station apparatus and the base station apparatus in a regenerative relay, wherein the non-regenerative relay is for amplifying a signal without regenerating the signal with a decoding-reencoding process, and the regenerative relay is for regenerating a signal with a decoding-reencoding process;

a measuring section configured to control measurement of the first channel quality using the first pilot signal transmitted in the non-regenerative relay, and to control measurement of the second channel quality using the second pilot signal transmitted in the regenerative relay;

a determining section configured to control determination of a relay scheme to be selected by the relay station apparatus, between the non-regenerative relay or the regenerative relay, based on the first channel quality in the non-regenerative relay and the second channel quality in the regenerative relay; and

a transmission section configured to control transmission of relay information indicating the determined relay scheme to the relay station apparatus.

24. The integrated circuit according to claim 23, further comprising a table providing a relationship between a combination of the first channel quality in the non-regenerative relay and the second channel quality in the regenerative relay and two relay schemes of the non-regenerative relay and the regenerative relay,

wherein the relay scheme is determined with reference to the table.