Wireless communication system

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 MS 2, 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 MS 2 and the RS) measured at the RS. The determination result is transmitted as relay information to the RS and to the MS 2 (a mobile station ( 2 )) through the RS. The MS 2 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.

The invention claimed is: 
     
       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 regenerating the signal with a decoding-reencoding process and performing a relay transmission of the amplified signal, and a second relay scheme of a regenerative relay for changing the modulation scheme of the signal according to a channel quality regenerating a signal with a decoding-reencoding process and performing the a relay transmission of the regenerated signal, and the relay station switches between selects from 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 configured to select from two relay schemes of a non-regenerative relay for amplifying a signal transmitted from a mobile station transmission apparatus without changing a modulation scheme regenerating the signal with a decoding-reencoding process and performing a relay transmission of the amplified signal, and a regenerative relay for changing the modulation scheme of the regenerating a signal transmitted from the mobile station transmission apparatus according to a channel quality with a decoding-reencoding process and performing the a relay transmission of the regenerated signal, the relay station apparatus comprising:
 an amplifying section amplifier that amplifies the signal transmitted from the mobile station transmission apparatus when the non-regenerative relay is employed; 
 a demodulation section decoder that demodulates decodes the signal transmitted from the mobile station transmission apparatus when the regenerative relay is employed; 
 a modulation sectionan encoder that modulatesreencodes the signal demodulatedsignal decoded by the demodulation section using a modulation scheme in accordance with the channel qualitydecoder to generate a regenerated signal; and  
 a transmission section transmitter that transmits the amplified signal amplified by the amplifying section or the regenerated 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 depending on a combination of a first channel quality in the non-regenerative relay and a second channel quality in the regenerative relay. 
 
     
     
       8. The relay station apparatus according to  claim 7 , further comprising:
 a receiving section receiver that receives a pilot signal for employment in channel quality measurement from the mobile station transmission apparatus; and 
 a measuring section that measures configured to measure a channel quality between the mobile station transmission 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 transmitter transmits the pilot signal to the base station a reception apparatus in the non-regenerative relay and transmits a new pilot signal for employment in the channel quality measurement to the base station reception apparatus. 
     
     
       10. The relay station apparatus according to  claim 8 , wherein the transmission section transmitter further transmits information indicating the measured channel quality to the base station a reception 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 transmission apparatus and the relay station apparatus is determined. 
     
     
       12. The relay station apparatus according to  claim 7 , further comprising a receiving section receiver 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 one of the two relay schemes is selected 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 one of the two relay schemes is selected 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 selects from two relay schemes of a non-regenerative relay for amplifying a signal without changing a modulation scheme regenerating the signal with a decoding-reencoding process and performing a relay transmission of the amplified signal, and a regenerative relay for changing the modulation scheme of the signal according to a channel quality regenerating a signal with a decoding-reencoding process and performing a relay transmission of the regenerated signal, 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. A communication method performed by a relay station apparatus, the communication method selecting 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 communication method comprising:
 amplifying the signal transmitted from the transmission apparatus when the non-regenerative relay is employed;   decoding the signal transmitted from the transmission apparatus when the regenerative relay is employed;   reencoding the decoded signal to generate a regenerated signal; and   transmitting 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.