More than one reissue application has been filed for the reissue of U.S. Pat. No. 7,912,423. The reissue applications are application Ser. No. 13/802,109 (the present application), Ser. Nos. 13/444,664, and 13/802,120; application Ser. Nos. 13/802,109 and 13/802,120 are continuations of patent application Ser. No. 13/444,664 Filed Apr. 11, 2012 now RE 44,200.
The present invention relates to a wireless communication system.
In recent years, wireless cellular systems typified by cellular telephone systems and the like have diversified their service patterns, and have been demanded to transmit large-capacity data such as static images, moving pictures and the like as well as speech data. To meet such demands, it has been studied actively to transmit large-capacity data using a high-frequency radio band.
In using high-frequency radio band, the degree of attenuation due to the transmission distance becomes a problem. In other words, high transmission rates are obtained at locations near the transmitting station, but only low transmission rates are achieved at locations a predetermined distance or more apart from the transmitting station. Accordingly, to consider the actual operations of the communication system, it is necessary to cover a service area by installing a large number of base stations. However, installation of a large number of base stations requires significant cost. From such circumstances, a technique is strongly demanded that implements large-capacity communication service without increasing the number of base stations to install.
There is multi-hop communication, as one of methods for expanding the service area of a base station. This technique is a communication technique where a relay station installed in the base station service area relays and transmits a signal of a mobile station out of the service area to the base station (for example, see Non-Patent Document 1).
Multi-hop communication is broadly divided into regenerative relay and non-regenerative relay. In regenerative relay, a relay station once demodulates and decodes a received signal, encodes and modulates the signal again using a modulation scheme and coding rate (Modulation and Coding Scheme: MCS) in accordance with channel quality, and then transmits the result. In contrast, in non-regenerative relay, the relay station amplifies a received signal and transmits the signal without change. In comparison with non-regenerative relay, regenerative relay provides an advantage of enabling a relay using an adequate MCS in accordance with channel quality, yet also has a disadvantage of increasing the delay due to relay. Meanwhile, non-regenerative relay provides an advantage of decreasing the delay due to relay yet also has a disadvantage of making the SNR degrade by amplifying noise. Non-patent Document 1: Hasegawa et al. “Multi-hop System for Adaptive Modulation using Regenerating Fixed Hop Stations” Technical Report of IEICE, October 2004, A/P 2004-189, RC52004-210, pp. 57-61.
In regenerative relay in multi-hop communication, the throughput may decrease as the number of mobile stations using a single relay station increases. For example, when mobile station 1 (MS1) is communicating with a base station (BS) via a relay station (RS) by regenerative relay as shown in
In view of these respects, it is an object of the present invention to provide a wireless communication system that maintains system throughput and prevents a decrease in user throughput in multi-hop communication.
In the wireless communication system of the present invention, a mobile station and a base station communicate via a relay station, and this wireless communication system adopts a configuration of switchingselecting from two relay schemes of non-regenerative relay for amplifying a signal without changing a modulation schemeregenerating the signal with a decoding-reencoding process and performing a relay transmission of the amplified signal, and a regenerative relay for changing a modulation scheme of a signal according to channel qualityregenerating a signal with a decoding-reencoding process and performing a relay transmission of the regenerated signal, based on a combination of channel quality in the non-regenerative relay and channel quality in the regenerative relay.
According to the invention, it is possible to maintain system throughput and prevent a decrease in user throughput.
Embodiments of the present invention will be descried below in detail with reference to accompanying drawings.
In this Embodiment, a base station determines the relay scheme and MCS taking into account both the channel quality of regenerative relay and the channel quality of non-regenerative relay.
Described first is an operation sequence in a multi-hop communication system according to this Embodiment. The operation sequence is shown in
Upon newly joining in, the MS2 transmits a pilot signal (non-regenerative relay pilot) for measuring channel quality between the MS2 and the BS via the RS (MS2-RS-BS channel quality) and a pilot signal (regenerative relay pilot 1) for measuring channel quality between the MS2 and the RS (MS2-RS channel quality), to the RS. At this point, the MS2 adds a flag indicative of non-regenerative relay pilot and a flag indicative of regenerative relay pilot 1 to these pilot signals. In addition, the transmission order of non-regenerative relay pilot and regenerative relay pilot 1 is not limited.
The RS receiving these two kinds of pilot signals performs non-regenerative relay pilot processing on non-regenerative relay pilot to transmit to the BS. In other words, the RS maintains the MCS and amplifies the non-regenerative relay pilot and transmits the result to the BS. Further, the RS measures the received quality (MS2-RS channel quality) of regenerative relay pilot 1, and transmits channel quality information to the BS. Furthermore, the RS transmits a new pilot signal (regenerative relay pilot 2) for measurement of channel quality of a channel between the RS and the BS (RS-BS channel quality) to the BS. At this point, the RS adds a flag indicative of regenerative relay pilot 2 to regenerative relay pilot 2.
Next, the BS measures the received quality (MS2-RS-BS channel quality) of the non-regenerative relay pilot. Further, the BS measures the received quality (RS-BS channel quality) of regenerative relay pilot 2. By this means, the BS obtains the MS2-RS-BS channel quality as the channel quality of non-regenerative relay, and obtains the RS-BS channel quality as the channel quality of regenerative relay. Furthermore, the BS obtains the MS2-RS channel quality as the channel quality of regenerative relay from the received channel quality information. Then, based on these three kinds of channel quality, the BS determines the relay scheme of the RS (whether the RS performs regenerative relay or non-regenerative relay) and MCS in multi-hop communication. The determination results are transmitted to the RS as relay information. Further, this relay information is also transmitted to the MS2 via the RS.
The MS2 encodes and modulates uplink data with the MCS based on the relay information and transmits the result to the RS.
The RS switches between non-regenerative relay and regenerative relay based on the relay information and relays uplink data. In other words, in the case of non-regenerative relay, the RS maintains the MCS, and amplifies uplink data and transmits the result to the BS. Meanwhile, in the case of regenerative relay, the RS once demodulates and decodes uplink data, and encodes and modulates the uplink data again with the MCS based on the relay information and transmits the result to the BS.
Described next is a configuration of the BS (base station) according to this Embodiment.
In BS 200 shown in
The channel quality information and the uplink data are demodulated in demodulation section 105 and decoded in decoding section 106 according to the MCS determined in determining section 104. The received data is thereby obtained. Further, the decoded channel quality information (MS2-RS channel quality) is inputted to determining section 104.
Meanwhile, received quality measuring section 103 measures the received quality of non-regenerative relay pilot and regenerative relay pilot 2, and obtains the MS2-RS-BS channel quality and RS-BS channel quality. These kinds of channel quality are inputted to determining section 104. In addition, received quality measuring section 103 is able to distinguish between the non-regenerative relay pilot and regenerative relay pilot 2 by the flags added to the pilot signals.
Determining section 104 determines the relay scheme of the RS and MCS in multi-hop communication from the MS2-RS-BS channel quality, MS2-RS channel quality and RS-BS channel quality. The determination method will be described later. The determination results (the relay scheme and MCS) are inputted to coding section 107 as relay information.
The relay information and the transmission data (downlink data) are encoded in coding section 107 and modulated in modulation section 108 according to the MCS determined in determining section 104. The modulated relay information and the downlink data are subjected to radio processing such as up-conversion in RF transmitting section 109 and then transmitted via antenna 101.
Described next is the method of determining the relay scheme and MCS. In addition, the received SNR is used as channel quality in the following descriptions.
First, determining section 104 classifies channel quality into three stages of “good”, “normal”, and “poor,” as shown in
Next, determining section 104 refers to a table as shown in
In
Described herein are grounds for generation of the table as shown in
First, the relationships between channel quality and MCS in regenerative relay are shown in the table of
Similarly, the relationships between channel quality and MCS in non-regenerative relay are shown in the table of
Herein, by comparing
Then, based on the table of
Accordingly, by selecting the combinations of relay schemes and MCS based on the table shown in
The configuration of the relay station (RS) according to this Embodiment will be described below.
In RS200 as shown in
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
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
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
In the table shown in
Further, when the MS2 is present in the service area of the BS, it is also possible to use a table as shown in
In the table shown in
In this Embodiment, in regenerative relay, the RS determines MCS between the MS and the RS.
Described first is an operation sequence in a multi-hop communication system according to this Embodiment. The operation sequence is shown in
Upon newly joining in, the MS2 transmits a pilot signal to measure both the MS2-RS channel quality and MS2-RS-BS channel quality to the RS. This pilot signal is a pilot shared between regenerative relay and non-regenerative relay, and so the flag for distinguishing between the regenerative relay pilot and the non-regenerative relay pilot is not added.
The RS receiving this pilot signal performs non-regenerative relay processing on the pilot to transmit to the BS as a non-regenerative relay pilot. In other words, the RS maintains the MCS and amplifies the pilot and transmits the result to the BS. At this point, the RS adds a flag indicative of non-regenerative relay pilot to non-regenerative relay pilot. Further, the RS measures the received quality (MS2-RS channel quality) of the received pilot, and, according to the channel quality, selects the MCS for between the MS2 and the RS in regenerative relay. The RS selects 16QAM when the channel quality is “good”, QPSK when the channel quality is “normal”, or BPSK when the channel quality is “poor”. The selection result is transmitted to the MS2 as MCS information. Further, the RS transmits a new pilot signal (regenerative relay pilot) to measure the RS-BS channel quality to the BS. At this point, the RS adds a flag indicative of regenerative relay pilot to regenerative relay pilot.
Next, the BS measures the received quality (MS2-RS-BS channel quality) of non-regenerative relay pilot. Further, the BS measures the received quality (RS-BS channel quality) of regenerative relay pilot. By this means, the BS obtains the MS2-RS-BS channel quality as the channel quality of non-regenerative relay, and further obtains the RS-BS channel quality as the channel quality of regenerative relay. Then, based on these two kinds of channel quality, the BS determines the relay scheme for the RS (whether the RS performs regenerative relay or non-regenerative relay), and further determines the MCS for between the RS and the BS in regenerative relay or determines the MCS for between the MS2 and the BS via the RS in non-regenerative relay. The determination result is transmitted to the RS as relay information. Further, this relay information is also transmitted to the MS2 via the RS.
In the case of regenerative relay, the MS2 performs coding and modulation on the uplink data with the MCS based on the MCS information transmitted from the RS to transmit to the RS. Meanwhile, in the case of non-regenerative relay, the MS2 performs coding and modulation on the uplink data with the MCS based on the relay information transmitted from the BS to transmit to the RS.
The RS switches non-regenerative relay and regenerative relay based on the relay information to relay the uplink data. In other words, in the case of non-regenerative relay, the RS maintains the MCS and amplifies the uplink data and transmits the result to the BS. Meanwhile, in the case of regenerative relay, the RS once demodulates and decodes the uplink data with the MCS determined by the RS, and performs coding and modulation again on the uplink data with the MCS based on the relay information to transmit to the BS. In addition, for the downlink data, in the case of regenerative relay, the RS once demodulates and decodes the downlink data from the BS, and performs coding and modulation again on the downlink data with the MCS determined by the RS to transmit to the MS2.
Described next is a configuration of the BS (base station) according to this Embodiment.
In BS 300 as shown in
The uplink data is demodulated in demodulation section 305 and decoded in decoding section 306 according to MCS determined in determining section 304. The received data is thereby obtained.
Meanwhile, received quality measuring section 303 measures the received quality of non-regenerative relay pilot and regenerative relay pilot, and obtains the MS2-RS-BS channel quality and RS-BS channel quality. These kinds of channel quality are inputted to determining section 304. In addition, received quality measuring section 303 is capable of distinguishing between the non-regenerative relay pilot and the regenerative relay pilot by the flag added to each pilot.
Determining section 304 determines the relay scheme of the RS and MCS from the MS2-RS-BS channel quality and RS-BS channel quality. The determination method will be described later. The determination results (relay scheme and MCS) are inputted to coding section 307 as relay information.
The relay information and transmission data (downlink data) are encoded in coding section 307 and modulated in modulation section 308 according to the MCS determined in determining section 304. The modulated relay information and downlink data are subjected to radio processing such as up-conversion in RF transmitting section 309, and transmitted via antenna 301.
Described next is the method of determining the relay scheme and MCS. In addition, the received SNR is used as channel quality in the following descriptions.
First, determining section 304 classifies channel quality into three stages, “good”, “normal”, and “poor,” as shown in
Next, determining section 304 refers to the table shown in
Based on the table of
Further, when regenerative relay is selected as the relay scheme that obtains optimal transmission rates based on
The configuration of the RS (relay station) according to this Embodiment will be described below.
In RS400 as shown in
Received quality measuring section 403 measures the received quality of the pilot, and obtains the MS2-RS channel quality.
Based on the MS2-RS channel quality, MCS determining section 404 determines the MCS for between the MS2 and the RS, and inputs MCS information to demodulation section 407 and decoding section 408. Further, the MCS information for between the MS2 and the RS is inputted to coding section 409 to be notified to the MS2.
Switching section 405 has a table (part of the table of
Amplifying section 406 amplifies uplink data and pilot to input to RF transmitting section 411.
Meanwhile, the uplink data inputted to demodulation section 407 is demodulated in demodulation section 407 and decoded in decoding 408 according to the MCS of MS2-RS designated by MCS determining section 404. The result is encoded again in coding section 409 and modulated again in modulation section 410 according to the MCS of RS-BS designated by switching section 405. The modulated uplink data is inputted to RF transmitting section 411.
Meanwhile, regenerative relay pilot and the MCS information of MS2-RS are encoded in coding section 409, modulated in modulation section 410, and inputted to RF transmitting section 411.
The uplink data (to be relayed in regenerative relay) inputted from modulation section 410 and the uplink data (to be relayed in non-regenerative relay) inputted from amplifying section 406 are subjected to radio processing such as up-conversion in RF transmitting section 411, and transmitted to the BS via antenna 401. Further, regenerative relay pilot, and the pilot (non-regenerative relay pilot) amplified in amplifying section 406 are also subjected to the radio processing such as up-conversion in RF transmitting section 411, and transmitted to the BS via antenna 401. Furthermore, the MCS information of MS2-RS is subjected to the radio processing such as up-conversion in RF transmitting section 411, and transmitted to the MS2 via antenna 401. In addition, the relay information is transmitted to the MS2 in the relay scheme of the downlink data switched in the same way as in the uplink data.
In addition, as in Embodiment 1, when multiplexing schemes such as CDM and SDM are used in communications between the MS and the RS, it is also possible to use the table shown in
Thus, according to this Embodiment, as in Embodiment 1, it is possible to improve system throughput, while preventing the user throughput from decreasing. Further, in this Embodiment, the RS determines the MCS for between the MS and the RS in regenerative relay. Therefore, as compared with Embodiment 1, it is possible to decrease the number of pilots that the MS transmits, while the need is eliminated of the RS transmitting the BS-RS channel quality to the BS, and the system throughput can thus be further increased.
In addition, in the above-mentioned Embodiment, each table is generated so as to maximize the transmission rate, but it is possible to generate each table according to various requirements of the communication system, such as “meeting a data rate of minimum 1 Mbps”, “transmission rate that meets BER=0.01 at SNR=15 dB”, and so on.
Further, although examples have been explained in the above-mentioned Embodiments where the base station determines the relay scheme and MCS, the relay station or mobile station may hold the reference table to determine the relay scheme and MCS.
Although with the above embodiments cases have been described where the present invention is configured by hardware, the present invention may be implemented by software.
Each function block employed in the description of each of the aforementioned embodiments may typically be implemented as an LSI constituted by an integrated circuit. These may be individual chips or partially or totally contained on a single chip.
“LSI” is adopted here but this may also be referred to as “IC”, “system LSI”, “super LSI”, or “ultra LSI” depending on differing extents of integration.
Further, the method of circuit integration is not limited to LSI's, and implementation using dedicated circuitry or general purpose processors is also possible. After LSI manufacture, utilization of an FPGA (Field Programmable Gate Array) or a reconfigurable processor where connections and settings of circuit cells within an LSI can be reconfigured is also possible.
Further, if integrated circuit technology comes out to replace LSI's as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Application of biotechnology is also possible.
The present application is based on Japanese Patent Application No.2005-071775, filed on Mar. 14, 2005, the entire content of which is expressly incorporated by reference herein.
The present invention is suitable for use in a mobile communication system using a high-frequency radio band.
Number | Date | Country | Kind |
---|---|---|---|
2005071775 | Mar 2005 | JP | national |
Filing Document | Filing Date | Country | Kind | 371c Date |
---|---|---|---|---|
PCT/JP2006/304901 | 3/13/2006 | WO | 00 | 12/10/2007 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2006/098273 | 9/21/2006 | WO | A |
Number | Name | Date | Kind |
---|---|---|---|
20040198467 | Orlik | Oct 2004 | A1 |
20050014464 | Larsson | Jan 2005 | A1 |
20070160014 | Larsson | Jul 2007 | A1 |
Number | Date | Country |
---|---|---|
2-295234 | Dec 1990 | JP |
2-295234 | Dec 1990 | JP |
4-196626 | Jul 1992 | JP |
4-196626 | Jul 1992 | JP |
2003-018059 | Jan 2003 | JP |
2003-18059 | Jan 2003 | JP |
2004107693 | Dec 2004 | WO |
2004107693 | Dec 2004 | WO |
Entry |
---|
Hasegawa et al., “Multi-hop System for Adaptive Modulation using Regenerating Fixed Hop Stations,” Technical Report of IEICE, A-P2004-189, RCS2004-210, Oct. 2004, pp. 57-61. |
International Search Report for corresponding International Patent Application No. PCT/JP2006/304901 dated May 16, 2006, 3 pages. |
Supplementary Search Report for corresponding EP Patent Application No. 06728966.0 dated Apr. 27, 2010, 3 pages. |
PCT International Search Report dated May 16, 2006. |
R. Hasegawa, et al.; “Multi-hop System for Adaptive Modulation using Regenerating Fixed Hop Stations,” Technical Report of IEICE, A-P2004-189, RCS2004-210, Oct. 2004, pp. 57-61. |
Supplementary European Search Report dated Apr. 27, 2008. |
International Search Report dated May 16, 2006. |
Number | Date | Country | |
---|---|---|---|
Parent | 13444664 | Apr 2012 | US |
Child | 11908486 | US |
Number | Date | Country | |
---|---|---|---|
Parent | 11908486 | Mar 2006 | US |
Child | 13802109 | US | |
Parent | 11908486 | Mar 2006 | US |
Child | 13444664 | US |