US20060084475A1 - Mobile communication systems, mobile communication methods, base stations, mobile stations, and signal transmission methods in the mobile communication systems - Google Patents

Abstract

A mobile station is configured to measure receiving qualities of respective signals from a first antenna and a second antenna of a base station (S3, S5), store the results of the measurement, and request the base station to retransmit a signal from an antenna with a higher receiving quality, based on the stored measurement results, when an error is detected in received data thereafter (S10, S11, S12). The base station retransmits the data, using the antenna with the higher receiving quality (i.e., a base station antenna to yield the higher receiving quality at the mobile station) (S15). In another aspect, the mobile station measures a receiving quality of a signal and notifies the base station of the receiving quality. The base station selects a radio channel adapted to a receiving quality on the basis of the measurement result and transmits a signal, using the radio channel.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS
• This application is a continuation of U.S. application Ser. No. 10/166,652 filed Jun. 12, 2002, and further is based upon and claims the benefit of priority from the Japanese Patent Application Nos. 2001-178999, filed Jun. 13, 2001, and 2001-186910, filed Jun. 20, 2001, the entire contents of each of which are incorporated herein by reference.
BACKGROUND OF THE INVENTION
• 1. Field of the Invention
• The present invention relates to mobile communication systems, mobile communication methods, base stations, and mobile stations and, more particularly, to a mobile communication system comprising a mobile station and a base station equipped with a plurality of antennas and configured to perform signal transmission/reception control including signal retransmission control by the base station on the basis of an automatic repeat request from the mobile station, a mobile communication method executed by the mobile communication system, and the base station and the mobile station constituting the mobile communication system.
• The present invention also relates to signal transmitting methods and systems in mobile communication systems and, more particularly, to a signal transmitting method and system in a mobile communication system configured to perform transmission/reception of a signal while transmitting and receiving an automatic repeat request, the signal transmitting method and system being configured to transmit the signal while changing channels one from another so as to improve the receiving quality at the mobile station.
• Further, the present invention relates to base stations that can perform communication according to the aforementioned signal transmitting methods.
• The present invention also relates to mobile stations performing communication according to the foregoing signal transmitting methods.
• 2. Related Background Art
• FIG. 1 is a block diagram of a conventionalmobile communication system10, andFIG. 2 a chart for explaining the cooperative operation of the conventional mobile communication system with an automatic repeat request. At abase station1, an ARQ (Automatic Repeat Request)processor2 accepts input data addressed to amobile station11 through adata input terminal6. TheARQ processor2 attaches error-detectable parity such as CRC (Cyclic Redundancy Checking code) or the like to the data so as to enable detection of an error occurring during transmission, thereafter stores the data (A1 inFIG. 2), and outputs the data to atransmitter3. Thetransmitter3 modulates the input data into a transmitted signal and then transmits the signal through a transmitted/receivedwave splitter4 and from a firstbase station antenna7 to themobile station11 through a downlink22 (A2).
• At themobile station11, areceiver12 receives the signal from amobile station antenna17 through a transmitted/receivedwave splitter16. Then the signal received at thereceiver12 is fed as received data to an ARQ processor13 (A3). TheARQ processor13 performs detection of error using the CRC (A4).
• When no error is detected in the received data herein, theARQ processor13 outputs the received data from adata output terminal14 and outputs an acknowledgement of arrival of the received data to atransmitter15. Thetransmitter15 transmits the acknowledgement of arrival of the received data to theARQ processor2 of thebase station1 through an uplink21 (A5). Receiving the arrival acknowledgement, theARQ processor2 deletes the data stored for retransmission (A7 and A8).
• When an error is detected in the received data at A4 on the other hand, theARQ processor13 sends a repeat request for retransmission of the received data to theARQ processor2 of thebase station1 through the uplink21 (A6). Receiving the repeat request, theARQ processor2 retransmits the requested data from the first base station antenna7 (A7 and A9).
• FIG. 3 andFIG. 4 are a block diagram of another conventional mobile communication system and a flowchart for explaining the operation thereof. As shown inFIG. 3, the conventional mobile communication system is comprised of abase station21 and amobile station31.
• Thebase station21 is generally comprised of an ARQ (Automatic Repeat Request)processor22, a transmitter/receiver23, asignal input terminal24, and abase station antenna25. Themobile station31 on the other hand is generally comprised of a transmitter/receiver32, anARQ processor33, asignal output terminal34, and amobile station antenna35.
• The operation of the conventional mobile communication system will be described below with reference to the flowchart ofFIG. 4.
• At thebase station21, the ARQprocessor22 receives an input signal addressed to themobile station31 through thesignal input terminal24. TheARQ processor22 attaches the error-detectable parity such as the CRC (Cyclic Redundancy Checking code) or the like to the data so as to enable detection of an error occurring during transmission, thereafter stores the signal (B1), and outputs the signal to the transmitter/receiver23. The transmitter/receiver23 informs the mobile station of a start of transmission of the signal (B2) and thereafter transmits the signal to themobile station31 through adownlink42 which is a frequency channel determined for transmission of the signal addressed to the mobile station (B3).
• At themobile station31, the transmitter/receiver32 receives the signal of thedownlink42 received by the mobile station antenna35 (B4) and thereafter the signal is fed into theARQ processor33. TheARQ processor33 performs the detection of error in the received signal, using the CRC. When no error is detected in the received signal (NO at B5), the received signal is outputted from thesignal output terminal34 and an acknowledgement of arrival of the received signal is transmitted to theARQ processor22 of the base station through an uplink41 (B6). After that, the ARQprocessor22 receiving the arrival acknowledgement deletes the signal stored for retransmission (NO at B8, and B9).
• When an error is detected in the received signal on the other hand (YES at B5), theARQ processor33 sends a repeat request for retransmission of the received signal to theARQ processor22 of the base station through the uplink41 (B7). Then theARQ processor22 receiving the repeat request retransmits the requested signal in the frequency channel used for the preceding transmission (YES at B8, and B10).
SUMMARY OF THE INVENTION
• In the method of transmitting the high-quality signal with the automatic repeat request in the conventional mobile communication system described with reference toFIGS. 1 and 2, however, since the signals were always transmitted with the use of the same base station antenna, a low receiving quality state due to fading or shadowing continued at a simple mobile station incapable of implementing receiving antenna diversity or at a mobile station staying long at an identical site, which posed the problem of degradation of throughput because of repetition of repeat requests.
• An object of the present invention is therefore to decrease the repetition of repeat requests from the mobile station, thereby enhancing the throughput.
• In order to achieve the above object, a mobile communication system according to the present invention is, as set forth inclaim1, a mobile communication system comprising a mobile station and a base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request, wherein the mobile station comprises: receiving quality measuring means for measuring a receiving quality of a radio signal transmitted from the base station; and request transmitting means for transmitting to the base station a radio resource use request for use of a radio resource adapted to a receiving quality, based on the measured receiving quality of the radio signal. The base station comprises: request receiving means for receiving the radio resource use request; and signal transmitting means for transmitting a signal addressed to the mobile station, including a signal under a request for retransmission by the automatic repeat request, using the radio resource requested by the radio resource use request.
• In the mobile communication system as set forth inclaim2, the signal transmitting means transmits the signal by using radio resources in decreasing order of the number of repeat requests from the mobile station.
• Further, in the mobile communication system as set forth inclaim3, the receiving quality is one selected from the following:
• a received power;
  C/(I+N)  (Eq. 1)
• C: carrier power
• I: interference power
• N: noise power;
  S/(I+N)  (Eq. 2)
• S: signal power
• I: interference power
• N: noise power;
  C/N  (Eq. 3)
• C: carrier power
• N: noise power;
  S/N  (Eq. 4)
• S: signal power
• N: noise power;
• an error rate;
• a likelihood obtained in decoding of error correction code;
• a transmission power value of the base station;
• an increase amount or an attenuation amount of the transmission power of the base station;
• a correlation value obtained by despreading of spreading code;
• either of combinations of these.
• In the mobile communication system as set forth inclaim4, the radio resource is at least one antenna, directivities of at least one antenna, a radio channel, a transmission path, or either of combinations of these. Here the antenna may be a single antenna or a plurality of antennas, and in the case of a plurality of antennas being used, directivities of the respective antennas may be different from each other. The transmission path is intended for a situation in which a signal is indirectly transmitted via a mobile station as a relay station (multihop connection).
• In order to achieve the above object, a mobile communication system according to the present invention is, as set forth inclaim2, a mobile communication system comprising a mobile station, and a base station equipped with a plurality of antennas, and configured to perform signal transmission/reception control including signal retransmission control by the base station on the basis of an automatic repeat request from the mobile station, wherein the mobile station comprises: quality measuring means for measuring receiving qualities of signals transmitted from the plurality of antennas of the base station; and request transmitting means for transmitting to the base station an antenna use request that a signal should be transmitted from at least one antenna out of the plurality of antennas, based on the receiving qualities of the signals from the respective antennas obtained by measurement, and wherein the base station comprises: request receiving means for receiving the antenna use request that the signal should be transmitted from at least one antenna out of the plurality of antennas; and signal transmitting means for transmitting a signal addressed to the mobile station, including the signal under the automatic repeat request for retransmission, from the antenna requested by the antenna use request.
• A mobile communication method according to the present invention is, as set forth inclaim11, a mobile communication method which is executed by a mobile communication system comprising a mobile station, and a base station equipped with a plurality of antennas, and which is configured to perform signal transmission/reception control including signal retransmission control by the base station on the basis of an automatic repeat request from the mobile station, the mobile communication method comprising: a quality measuring step of, at the mobile station, measuring receiving qualities of signals transmitted from the plurality of antennas of the base station; a request transmitting step of, at the mobile station, transmitting to the base station an antenna use request that a signal should be transmitted from at least one antenna out of the plurality of antennas, based on the receiving qualities of the signals from the respective antennas obtained by the measurement; a request receiving step of, at the base station, receiving the antenna use request that the signal should be transmitted from at least one antenna out of the plurality of antennas; and a signal transmitting step of, at the base station, transmitting a signal addressed to the mobile station, including the signal under the automatic repeat request for retransmission, from the antenna requested by the antenna use request.
• A base station according to the present invention is, as set forth inclaim17, a base station which is equipped with a plurality of antennas, constituting a mobile communication system, together with a mobile station requesting to transmit a signal from at least one antenna out of the plurality of antennas on the basis of receiving qualities of signals transmitted from the plurality of antennas, and which is configured to perform, with the mobile station, signal transmission/reception control including signal retransmission control based on an automatic repeat request from the mobile station, the base station comprising: request receiving means for receiving an antenna use request that a signal should be transmitted from at least one antenna out of the plurality of antennas; and signal transmitting means for transmitting a signal addressed to the mobile station, including the signal under the automatic repeat request for retransmission, from the antenna requested by the antenna use request.
• A mobile station according to the present invention is, as set forth inclaim21, a mobile station which is configured to perform signal transmission/reception control including signal retransmission control based on an automatic repeat request, with a base station equipped with a plurality of antennas and configured to transmit a signal on the basis of a signal transmission request from at least one antenna out of the plurality of antennas, the mobile station comprising: quality measuring means for measuring receiving qualities of signals transmitted from the plurality of antennas of the base station; and request transmitting means for transmitting to the base station an antenna use request that a signal should be transmitted from at least one antenna out of the plurality of antennas, based on the receiving qualities of the signals from the respective antennas obtained by measurement.
• Incidentally, the foregoing mobile communication system, mobile communication method, base station, and mobile station according to the present invention are based on the same technical concept and they are aspects of the same technical concept as a mobile communication system, as a mobile communication method, as a base station, and as a mobile station.
• The following will describe the means for solving the problem in the mobile communication system according to the present invention, but it is noted that the means for solving the problem in the mobile communication method, the base station, and the mobile station are also based on the same concept.
• In the mobile communication system according to the present invention, at the mobile station the quality measuring means measures the receiving qualities of the signals transmitted from the plurality of antennas of the base station and the request transmitting means transmits to the base station the antenna use request that the signal should be transmitted from at least one antenna out of the plurality of antennas, based on the receiving qualities of the signals from the respective antennas acquired by the measurement. Namely, this request transmitting means transmits to the base station the antenna use request that the base station should transmit the signal from at least one antenna with the receiving quality of the signal better than those from the other antennas.
• At the base station, the request receiving means receives the antenna use request from the foregoing mobile station, and then the signal transmitting means transmits the signal addressed to the mobile station, including the signal under the automatic repeat request for retransmission, from the antenna requested by the antenna use request.
• Through this operation, the signal addressed to the mobile station is transmitted from at least one antenna with the receiving quality relatively better, based on the receiving qualities of the signals measured at the mobile station, and it is thus feasible to improve the receiving quality of the signal at the mobile station, to prevent the repetition of repeat requests from the mobile station, and to enhance the throughput.
• The foregoing mobile communication system can also be applied to transmission of a multicast signal addressed to a plurality of mobile stations.
• Namely, a mobile communication system as set forth inclaim6 is configured so that at the mobile station the quality measuring means measures receiving qualities of signals transmitted from the plurality of antennas of the base station and the request transmitting means transmits to the base station an antenna use request that a multicast signal should be transmitted from at least one antenna out of the plurality of antennas, based on the receiving qualities of the signals from the respective antennas acquired by the measurement. Namely, this request transmitting means transmits to the base station the antenna use request that the base station should transmit the multicast signal from at least one antenna with the receiving quality of the signal better than those from the other antennas.
• At the base station the request receiving means receives the antenna use request from the mobile station, and then multicast signal transmitting means transmits a multicast signal addressed to the mobile station, including the multicast signal under the automatic repeat request for retransmission, from the antenna requested by the antenna use request.
• Through this operation, the multicast signal addressed to the mobile station is transmitted from at least one antenna with the receiving quality relatively better, based on the receiving qualities of the signals measured at the mobile station, and it is thus feasible to improve the receiving quality of the multicast signal at the mobile station, to prevent the repetition of repeat requests from the mobile station, and to enhance the throughput.
• In the foregoing configuration, however, there can occur cases where the antenna use requests from a plurality of mobile stations are present over two or more antennas, but the system can be configured, as set forth inclaim7, so that when antenna use requests from a plurality of mobile stations are present over two or more antennas, the multicast signal transmitting means transmits the multicast signal, using the antennas in descending order of the number of requests. In this configuration, as the entire system, it is feasible to improve the receiving quality of the multicast signal at more mobile stations, to decrease the total number of occurrences of repeat requests, and to enhance the total throughput of the entire system.
• The invention as set forth inclaims6 and7 can be described as follows from the view points of the mobile communication method, the base station, and the mobile station.
• Namely, a mobile communication method as set forth inclaim12 is a mobile communication method which is executed by a mobile communication system comprising a plurality of mobile stations, and a base station equipped with a plurality of antennas and which is configured to perform signal transmission/reception control including signal retransmission control by the base station on the basis of an automatic repeat request from a mobile station, the mobile communication method comprising: a quality measuring step of, at the mobile station, measuring receiving qualities of signals transmitted from the plurality of antennas of the base station; a request transmitting step of, at the mobile station, transmitting to the base station an antenna use request that a multicast signal should be transmitted from at least one antenna out of the plurality of antennas, based on the receiving qualities of the signals from the respective antennas obtained by the measurement; a request receiving step of, at the base station, receiving the antenna use request that the multicast signal should be transmitted from at least one antenna out of the plurality of antennas; and a multicast signal transmitting step of, at the base station, transmitting a multicast signal addressed to the mobile station, including the multicast signal under the automatic repeat request for retransmission, from the antenna requested by the antenna use request.
• A mobile communication method as set forth inclaim13 is the mobile communication method according toclaim12, wherein in the multicast signal transmitting step, when antenna use requests from the plurality of mobile stations are present over two or more antennas, the base station transmits the multicast signal by using the antennas in descending order of the number of requests.
• A base station as set fort in claim18 is a base station which is equipped with a plurality of antennas, constituting a mobile communication system, together with a plurality of mobile stations requesting to transmit a multicast signal from at least one antenna out of the plurality of antennas on the basis of receiving qualities of signals transmitted from the plurality of antennas, and which is configured to perform, with the mobile stations, signal transmission/reception control including multicast signal retransmission control based on an automatic repeat request from the mobile stations, the base station comprising: request receiving means for receiving an antenna use request that a multicast signal should be transmitted from at least one antenna out of the plurality of antennas; and multicast signal transmitting means for transmitting a multicast signal addressed to the mobile station, including the multicast signal under the automatic repeat request for retransmission, from the antenna requested by the antenna use request.
• A base station as set forth in claim19 is the base station according to claim18, wherein when antenna use requests from the plurality of mobile stations are present over two or more antennas, the multicast signal transmitting means transmits the multicast signal by using the antennas in decreasing order of the number of requests.
• A mobile station as set forth inclaim22 is a mobile station which is configured to perform signal transmission/reception control including multicast signal retransmission control based on an automatic repeat request, with a base station equipped with a plurality of antennas and configured to transmit a multicast signal on the basis of a signal transmission request from at least one antenna out of the plurality of antennas, the mobile station comprising: quality measuring means for measuring receiving qualities of signals transmitted from the plurality of antennas of the base station; and request transmitting means for transmitting to the base station an antenna use request that a multicast signal should be transmitted from at least one antenna out of the plurality of antennas, based on the receiving qualities of the signals from the respective antennas obtained by measurement.
• The foregoing mobile communication system as set forth inclaim5 or6 is preferably configured, as set forth inclaim8, so that when receiving the antenna use request, the request receiving means of the base station performs antenna reception in a diversity system. The diversity reception is generally classified under three methods, the selection combining method using a signal from an antenna with the maximum level out of a plurality of antennas, the equal-gain combining method of combining outputs from the plurality of antennas as they are, and the maximal-ratio combining method of combining outputs with respective weights according to their levels. The request receiving means of the base station may employ any one of these methods. By performing the antenna reception by these diversity methods, it is feasible to implement stable reception of the antenna use request.
• Likewise, a mobile communication method as set forth inclaim14 is the mobile communication method according to claim11 or12 wherein in the request receiving step, when receiving the antenna use request, the base station performs antenna reception in a diversity system. A base station as set forth in claim20 is the base station according to claim17 or18 wherein when receiving the antenna use request, the request receiving means performs antenna reception in a diversity system.
• In the mobile communication system as set forth in one ofclaims5 to8, when at the mobile station the quality measuring means measures the receiving qualities of the signals transmitted from the plurality of antennas of the base station, the signals as measured objects are not limited to specific signals, but can be selected from various signals. Specifically, as set forth inclaim9, the quality measuring means can measure the receiving quality by using a synchronization signal, a signal of annunciation information, an individual signal to the mobile station, a multicast signal, or a combination of two or more out of these signals, transmitted from at least one antenna of the base station.
• Likewise, a mobile communication method as set forth inclaim15 is the mobile communication method according to either one ofclaims11 to14, wherein in the quality measuring step, the mobile station measures the receiving quality by using a synchronization signal, a signal of annunciation information, an individual signal to the mobile station, a multicast signal, or a combination of two or more out of these, transmitted from at least one antenna of the base station. A mobile station as set forth inclaim23 is the mobile station according to claim21 or22 wherein the quality measuring means measures the receiving quality by using a synchronization signal, a signal of annunciation information, an individual signal to the mobile station, a multicast signal, or a combination of two or more out of these signals, transmitted from at least one antenna of the base station.
• The physical quantity used as the receiving quality measured at this time is not limited to a specific physical quantity, either, but it can be selected from various physical quantities. Specifically, as set forth inclaim10, the receiving quality can be a received power, a value obtained by dividing a carrier power by the sum of an interference power and a noise power (C/(I+N)), a value obtained by dividing a signal power by the sum of an interference power and a noise power (S/(I+N)), an error rate, a likelihood obtained in decoding of error correction code, a C/N ratio (Carrier to Noise Ratio), an S/N ratio (Signal to Noise Ratio), a correlation value obtained by despreading of spreading code, or a combination of two or more out of these.
• Likewise, a mobile communication method as set forth inclaim16 is the mobile communication method according to either one ofclaims11 to15 wherein the receiving quality is a received power, a value obtained by dividing a carrier power by the sum of an interference power and a noise power, a value obtained by dividing a signal power by the sum of an interference power and a noise power, an error rate, a likelihood obtained in decoding of error correction code, a C/N ratio, an S/N ratio, a correlation value obtained by despreading of spreading code, or a combination of two or more out of these. A mobile station as set forth inclaim24 is the mobile station according to either one ofclaims21 to23 wherein the receiving quality is a received power, a value obtained by dividing a carrier power by the sum of an interference power and a noise power, a value obtained by dividing a signal power by the sum of an interference power and a noise power, an error rate, a likelihood obtained in decoding of error correction code, a C/N ratio, an S/N ratio, a correlation value obtained by despreading of spreading code, or a combination of two or more out of these.
• According to the present invention, as described above, the signal addressed to the mobile station (including the multicast signal) is transmitted from at least one antenna with the receiving quality relatively better, based on the receiving qualities of the signals measured at the mobile station, and it is thus feasible to improve the receiving quality of the signal at the mobile station, to prevent the repetition of repeat requests from the mobile station, and to enhance the throughput.
• When the present invention is applied in combination with site diversity, use of plural base stations provides the effect of increasing the diversity gain against shadowing, and the control time can be unlimitedly shortened by the feature of the present invention of using plural antennas in one base station. This makes it feasible to realize large diversity gain against fading. The maximum diversity gain can be achieved by applying the site diversity to the present invention in this way.
• In the conventional mobile communication system, as described with reference toFIGS. 3 and 4, the base station transmits the signal in only the determined frequency channel for transmission of the signal addressed to the mobile station. Therefore, a simple mobile station incapable of implementing receiving antenna diversity, or a mobile station staying long at an identical site remained in a low receiving quality state due to fading or shadowing, thus posing the problem of degrading the throughput because of the repetition of repeat requests.
• An object of the present invention is therefore to decrease the repetition of repeat requests from the mobile station to enhance the throughput, as described above.
• In order to accomplish the above object, the present invention provides, as set forth inclaim25, a signal transmitting method in a mobile communication system comprising a mobile station and a base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request, the signal transmitting method being carried out as follows in the mobile communication system: the mobile station measures a receiving quality of a radio signal transmitted from the base station, the mobile station notifies the base station of the receiving quality of the radio signal thus measured, and the base station transmits a signal under a repeat request from the mobile station so as to meet a required receiving quality of the mobile station, based on the receiving quality thus notified of.
• According to the present invention, the base station transmits the signal under the repeat request from the mobile station so as to meet the required receiving quality at the mobile station, based on the receiving quality of the radio signal notified of by the mobile station, and it is thus feasible to avoid the continuation of the low receiving quality state due to fading or shadowing as suffered before. As a consequence, the repetition of repeat requests from the mobile station can be decreased, and it is feasible to enhance the throughput.
• Concerning the radio signal from the base station measured at the mobile station, as set forth in claim26, the signal transmitting method is configured so that the radio signal transmitted from the base station becomes at least one radio channel.
• A type of the radio channel from the base station measured at the base station is selected, for example, as set forth in claim27, so that the mobile station uses, as a radio channel for measurement of the receiving quality, an annunciation information channel or an individual channel or a multicast channel or a combination of these, among said at least one radio channel transmitted from the base station.
• According to the present invention, any radio channel can be used for the measurement of the receiving quality at the mobile station as long as it is a radio channel transmitted from the base station.
• The receiving quality of the radio channel measured at the mobile station is selected as in the signal transmitting method, as set forth in claim28; the receiving quality is one selected from the following:
• a received power;
  C/(I+N)  (Eq. 1)
• C: carrier power
• I: interference power
• N: noise power;
  S/(I+N)  (Eq. 2)
• S: signal power
• I: interference power
• N: noise power;
  C/N  (Eq. 3)
• C: carrier power
• N: noise power;
  S/N  (Eq. 4)
• S: signal power
• N: noise power;
• an error rate;
• a likelihood obtained in decoding of error correction code;
• a transmission power value of the base station;
• an increase amount or an attenuation amount of the transmission power of the base station;
• either of combinations of these.
• Further, radio channels used in radio transmission between the mobile station and the base station are selected as in the signal transmission method, as set forth in claim29, wherein radio channels transmitted and received between the base station and the mobile station are at least one of subcarrier channels, orthogonal subcarrier channels, frequency channels, and frequency channels in different frequency bands.
• According to the present invention, the radio channels are selected depending upon the transmission methods for transmission/reception of signals between the base station and the mobile station: the subcarrier channels in the multicarrier transmission system; the orthogonal subcarrier channels in the OFDM transmission system; the frequency channels in the FDM transmission system; the frequency channels in different frequency bands in the multiband transmission system.
• From the viewpoint of enabling the notification of the measured receiving quality on the occasion of the mobile station sending the repeat request to the base station, the present invention provides, as set forth in claim30, the signal transmitting method wherein when a repeat request for retransmission of a received signal is needed, the mobile station notifies the base station of the repeat request, together with the receiving quality of the radio signal measured.
• From the viewpoint of enabling the notification of the measured receiving quality on the occasion of the mobile station sending an arrival acknowledgement of a received packet to the base station, the present invention provides, as set forth inclaim31, the signal transmitting method wherein on an occasion of notifying the base station of an acknowledgement of arrival of a received signal, the mobile station notifies the base station of the receiving quality of said at least one radio channel measured.
• The information on the receiving quality sent from the mobile station to the base station is one as in the signal transmitting method, as set forth inclaim32, wherein the mobile station notifies the base station of a number of at least one radio channel and a receiving quality of the radio channel, or of only a channel number of a receiving quality within a predetermined range, as the receiving quality of said at least one radio channel measured.
• The information on the receiving quality is one as in the signal transmitting method, as set forth inclaim33, wherein the mobile station notifies the base station of a number of at least one radio channel satisfying a required receiving quality, including a radio channel with a maximum receiving quality at the mobile station, together with the receiving quality achieved.
• From the viewpoint of transmitting signals by changing radio channels used for transmission of signals so as to improve the receiving quality at the mobile station, the present invention provides, as set forth inclaim34, the signal transmitting method wherein the base station determines a radio channel satisfying the required receiving quality at the mobile station on the basis of notification from the mobile station, and the base station transmits a signal under a repeat request from the mobile station, using the radio channel determined.
• According to the present invention, the base station transmits the signal under the repeat request from the mobile station by changing the radio channels one from another so as to permit the mobile station receive the signal with the required receiving quality, based on the receiving quality notified of by the mobile station, and thus the base station does not always have to use the predetermined radio channel for transmission of the signal addressed to the mobile station, different from the conventional systems. Namely, the base station adaptively changes the radio channels one from another so as to improve the receiving quality at the mobile station, so that the mobile station becomes able to receive the signal with a better receiving quality, resulting in decreasing the repetition of repeat requests. In conjunction therewith, it becomes feasible to enhance the throughput.
• From the viewpoint that after the change of the radio channel as described above the base station also transmits a signal addressed to the mobile station through the use of the radio channel, so as to enable maintenance of the required receiving quality at the mobile station, the present invention provides, as set forth inclaim35, the signal transmitting method wherein after transmitting the signal under the repeat request from the mobile station, using the determined radio channel, the base station also transmits a signal addressed to the mobile station, using the determined radio channel.
• From the viewpoint of decreasing interference with other mobile stations, the present invention provides, as set forth in claim36, the signal transmitting method wherein, based on the notification from the mobile station, the base station determines a number of a radio channel which satisfies the required receiving quality at the mobile station and through which the signal is transmitted so that a transmission power from the base station becomes a predetermined value, and also determines a transmission power of the radio channel.
• According to the present invention, when receiving a repeat request from the mobile station, the base station transmits the signal requested by the repeat request, using the radio channel satisfying the required receiving quality at the mobile station and maintaining the transmission power from the base station at a predetermined value. Accordingly, when the predetermined value is set at a minimum value, the mobile station can receive the signal requested by the repeat request, with the required receiving quality even if the transmission power from the base station is minimum. Namely, since the signal is transmitted at the minimum transmission power from the base station, it is feasible to reduce the interference with the other mobile stations not receiving the signal under the repeat request.
• From the viewpoint of improving the receiving quality of the signal received at the mobile station even in the multicast transmission of transmitting an identical signal to a plurality of mobile stations, the present invention provides, as set forth in claim37, the signal transmitting method wherein when the base station transmits an identical multicast signal to a plurality of mobile stations, the base station determines a number of at least one radio channel which satisfies the required receiving quality at each mobile station and through which the multicast signal is transmitted so that a transmission power from the base station becomes a predetermined value, and also determines a transmission power of the radio channel, based on notification from each mobile station.
• The present invention also provides, as set forth in claim38, the signal transmitting method wherein when the base station transmits the identical multicast signal to the plurality of mobile stations, the base station determines a number of a radio channel that can be assumed to have the greatest number of repeat requests from the mobile stations, out of channel numbers with receiving qualities within a predetermined range, notified of by the respective mobile stations.
• Further, the present invention provides, as set forth in claim39, a mobile communication system comprising a mobile station and a base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request, wherein the mobile station comprises: receiving quality measuring means for measuring a receiving quality of a radio signal transmitted from the base station; and receiving quality notifying means for notifying the base station of the receiving quality of the radio signal thus measured, and wherein the base station comprises: transmitting means for transmitting a signal under a repeat request from the mobile station so that a required receiving quality is satisfied at the mobile station, based on the receiving quality notified of by the mobile station.
• The mobile communication system as set forth inclaim1 is different from the mobile communication system as set forth in claim39 in that the subject for determining the radio resource on the basis of the receiving quality is on the mobile station side in the former or on the base station side in the latter, and they both belong to the same technical concept.
• The present invention also provides, as set forth in claim56, a base station in a mobile communication system comprising a mobile station and the base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request, the base station comprising transmitting means for transmitting a signal under a repeat request from the mobile station so that a required receiving quality is satisfied at the mobile station, based on a receiving quality notified of by the mobile station.
• Further, the present invention provides, as set forth in claim63, a mobile station in a mobile communication system comprising the mobile station and a base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request, the mobile station comprising: receiving quality measuring means for measuring a receiving quality of a radio signal transmitted from the base station; and receiving quality notifying means for notifying the base station of the receiving quality of the radio signal thus measured.
• The present invention will become more fully understood from the detailed description given hereinbelow and the accompanying drawings which are given by way of illustration only, and thus are not to be considered as limiting the present invention.
• Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.
• A mobile communication system according to the present invention is configured, as set forth in claim53, so that the base station comprises radio resource determining means for determining a radio resource satisfying the required receiving quality at the mobile station on the basis of notification from the mobile station; and signal transmitting means for transmitting the signal under the repeat request from the mobile station, using the radio resource determined by the radio resource determining means.
• Further, in the mobile communication system as set forth in claim54, the transmitting means transmits the signal by using radio resources in decreasing order of the number of repeat requests from the mobile station.
• In the mobile communication system as set forth in claim55, the radio resource is at least one antenna, directivities of at least one antenna, a radio channel, a transmission path, or either of combinations of these. Here the antenna may be a single antenna or a plurality of antennas, and in the case of a plurality of antennas being used, directivities of the respective antennas may be different from each other. The transmission path is intended for a situation in which a signal is indirectly transmitted via a mobile station as a relay station (multihop connection).
BRIEF DESCRIPTION OF THE DRAWINGS
• FIG. 1 is a block diagram of a conventional mobile communication system.
• FIG. 2 is a chart for illustrating the cooperative operation of the conventional mobile communication system with the automatic repeat request.
• FIG. 3 is a block diagram of another conventional mobile communication system with the automatic repeat request.
• FIG. 4 is a chart for illustrating the operation of the conventional mobile communication system.
• FIG. 5 is a block diagram of a mobile communication system in the first embodiment of the present invention.
• FIG. 6 is a chart for illustrating the cooperative operation of the mobile communication system with the automatic repeat request in the first embodiment of the present invention.
• FIG. 7A is a diagram for illustrating the procedure of data transmission in application of the TDM system, andFIG. 7B a diagram for illustrating the procedure of data transmission in application of the CDM system.
• FIG. 8 is a block diagram of a mobile communication system in the second embodiment of the present invention.
• FIG. 9 is a chart for illustrating the cooperative operation of the mobile communication system with the automatic repeat request in the second embodiment of the present invention.
• FIG. 10 is a block diagram of a mobile communication system in the third embodiment to which the signal transmitting method of the present invention is applied.
• FIG. 11 is a flowchart showing the operation in the third embodiment of the present invention.
• FIG. 12 is a block diagram of a mobile communication system in the fourth embodiment to which the signal transmitting method of the present invention is applied.
• FIG. 13 is a flowchart showing the operation in the fourth embodiment of the present invention.
• FIG. 14 is a flowchart showing the processing procedure of determining a number of a frequency channel and a transmission power of the frequency channel in the fourth embodiment of the present invention.
• FIG. 15 is a diagram showing an example of receiving qualities of respective frequency channels at each of mobile stations in the fourth embodiment of the present invention.
• FIG. 16 is a block diagram of a mobile communication system in the fifth embodiment to which the signal transmitting method of the present invention is applied.
DESCRIPTION OF THE PREFERRED EMBODIMENTSFirst Embodiment
• The first embodiment of the present invention will be described with reference to FIGS.5 to7. The present embodiment will describe an example in which a base station is equipped with two base station antennas, but it is noted that the present invention can be substantiated with any number of base station antennas.
• First, the configuration of the mobile communication system will be generally described. As shown inFIG. 5, themobile communication system100 is generally comprised of abase station101 and amobile station111.
• Thebase station101 comprises a plurality ofbase station antennas7,8; a plurality of transmitted/receivedwave splitters4 provided corresponding to the respective antennas; anantenna switching unit109 for switching the transmitted/receivedwave splitters4 one from another to use either one; anARQ processor102 configured to perform various processes including a process of attaching the error-detectable parity such as the CRC or the like to the input data entering adata input terminal6, a process of retransmitting a signal in response to a repeat request from the mobile station, a process of notifying atransmitter103 of use of an antenna based on an antenna use request, and so on; thetransmitter103 configured to switch output of theantenna switching unit109 and transmit data from theARQ processor102; and areceiver5 configured to receive data from the outside through thebase station antennas7,8 and feed the data to theARQ processor102.
• Themobile station111 comprises amobile station antenna17; a transmitted/receivedwave splitter16; a receivingquality measuring unit118 configured to measure a receiving quality of a received signal for measurement of receiving quality and store the receiving quality in amemory119; areceiver12 configured to receive a signal from the outside through the transmitted/receivedwave splitter16; anARQ processor113 configured to perform the error detection using the CRC for the signal received at thereceiver12 and output data from adata output terminal14 and also configured to, with detection of an error, output to atransmitter15 notification of a repeat request for retransmission of received data and a number of a base station antenna with a high receiving quality; and atransmitter15 configured to transmit the notification of the repeat request and the number of the base station antenna with the high receiving quality from theARQ processor13.
• The present embodiment will be described hereinafter, supposing the receiving quality is a received power. However, as explicitly stated inclaim10, it is also possible to employ as the receiving quality a value obtained by dividing a carrier power by the sum of an interference power and a noise power (i.e., C/(I+N)), a value obtained by dividing a signal power by the sum of an interference power and a noise power (i.e., S/(I+N)), an error rate, a likelihood obtained in decoding of error correction code, a C/N ratio, an S/N ratio, a correlation value obtained by despreading of spreading code, or a combination of two or more out of these.
• The following will describe the operation of the mobile communication system alongFIG. 6.
• At thebase station101, data addressed to themobile station111, entering thedata input terminal6, is fed into theARQ processor102. TheARQ processor102 attaches the error-detectable parity such as the CRC or the like to the data so as to permit detection of an error occurring during transmission, thereafter stores the data, and outputs the data to the transmitter103 (step1).
• Prior to transmission of a transmitted signal of the input data, thetransmitter103 switches the output of theantenna switching unit109 to the first base station antenna and outputs a signal for measurement of receiving quality therefrom. The signal for measurement of receiving quality is transmitted through the transmitted/receivedwave splitter4 and from the firstbase station antenna7 to the mobile station111 (step2).
• At themobile station111, the signal for measurement of receiving quality is fed through the transmitted/receivedwave splitter16 into the receivingquality measuring unit118. The receivingquality measuring unit118 measures a received power value of the signal for measurement of receiving quality and stores the received power value as a receiving quality with the use of the first base station antenna in the memory119 (step3).
• Next, the output of theantenna switching unit109 is switched to the second base station antenna and a signal for measurement of receiving quality is outputted. The signal for measurement of receiving quality is transmitted through the transmitted/receivedwave splitter4 and from the secondbase station antenna8 to the mobile station111 (step4).
• At themobile station111, in much the same manner as above, the signal for measurement of receiving quality is fed through the transmitted/receivedwave splitter16 into the receivingquality measuring unit118 to measure a received power value thereof, and the received power value is stored as a receiving quality with the use of the second base station antenna in the memory119 (step5).
• Thereafter, as shown inFIG. 7A, the output of theantenna switching unit109 is switched to the firstbase station antenna7 and the transmitted signal of the data is outputted. The transmitted signal is transmitted through the transmitted/receivedwave splitter4 and from the firstbase station antenna7 to the mobile station111 (step6).
• The above described an application of the TDM (Time Division Multiple) system, but it is also possible to apply the CDM (Code Division Multiple) system. In this system, as shown inFIG. 7B, signals for measurement of receiving quality are spread by spreading codes uniquely corresponding to the respective antennas and thereafter the signals are transmitted from the corresponding antennas. The mobile station receives the signals, despreads the signals by the spreading codes uniquely corresponding to the antennas to obtain received powers, correlation values, or the like, and can use them as receiving qualities.
• The following will continue the description back into the application case of the TDM system.
• At themobile station111, the received signal is fed through the transmitted/receivedwave splitter16 into thereceiver12. Then the signal received at thereceiver12 is fed as received data into the ARQ processor113 (step7). Then theARQ processor113 performs the error detection using the CRC. When no error is detected in the received data herein, the received data is outputted from thedata output terminal14 and an acknowledgement of arrival of the data is sent through anuplink21 to theARQ processor102 of the base station101 (step8 and step9).
• Thebase station101 can be configured to, on the occasion of receiving notification of an arrival acknowledgement or a repeat request from themobile station111, feed the outputs from the firstbase station antenna7 and the secondbase station antenna8 into thereceiver5 and perform antenna reception in the diversity system of two branches, thereby improving the receiving quality of the uplink. Then theARQ processor102, receiving the notification of the arrival acknowledgement, deletes the data stored for retransmission (step13 and step14).
• When atstep8 an error is detected in the received data on the other hand, theARQ processor113 searches for a number of a base station antenna with the higher receiving quality, i.e., the higher received power value stored in thememory119, and outputs the number of the base station antenna together with a repeat request for retransmission of the received data to thetransmitter15. Thetransmitter15 sends the repeat request of the received data and the number of the base station antenna through theuplink21 to theARQ processor102 of the base station101 (step10,step11, and step12). TheARQ processor102, receiving the notification of the repeat request, first notifies thetransmitter103 of the antenna number requested by themobile station111, and thetransmitter103 controls theantenna switching unit109 so as to be ready for transmission through the use of the antenna to themobile station111. Then the data under the repeat request is retransmitted from the antenna requested by the mobile station111 (step13 and step15).
• Since theARQ processor102 stores the number of the antenna requested by themobile station111, it becomes feasible to transmit new data addressed to themobile station111, entering thedata input terminal6 thereafter, through the use of the base station antenna with the higher receiving quality at themobile station111, without the need for transmitting the aforementioned signals for measurement of receiving quality from thebase station101.
• According to the first embodiment as described above, the signal addressed to themobile station111 is transmitted from thebase station101 through the use of the antenna with the receiving quality relatively better, based on the receiving qualities of the signals measured at themobile station111, and it is thus feasible to improve the receiving quality of the signal at themobile station111, to prevent the repetition of repeat requests from themobile station111, and to enhance the throughput of themobile communication system100.
• The above described the transmission of the signals for measurement of receiving quality prior to the transmission of data, but the present invention can also be substantiated without the transmission of the signals for measurement of receiving quality prior to the data transmission, as stated inclaim9, by a configuration wherein themobile station111 receives a synchronization signal, a signal of annunciation information, an individual signal to the mobile station, a multicast signal, or a combination of two or more out of these and always updates the contents stored in thememory119.
• The present embodiment can also be applied to the mobile station functioning as a relay station instead of the base station, supposing the situation of multihop connection. In this case, themobile station111, which is a transmitting station of a repeat request, preliminarily identifies existence of an adjoining mobile station as relay station and requests retransmission of a signal by designating a transmission path including the mobile station (relay station). Similarly, thebase station101, which is a transmitting station of the signal according to the repeat request, preliminarily identifies existence of an adjoining mobile station as a relay station and responds to the repeat request by designating a transmission path including the mobile station (relay station).
Second Embodiment
• The configuration of the second embodiment of the present invention will be described with reference toFIG. 8.
• The present embodiment will describe an example of multicast transmission wherein the base station transmits identical data (which will be referred to as multicast data in the present embodiment) to a plurality of mobile stations and a configuration wherein an automatic repeat request is arranged so that notification of a repeat request is given only when an error is detected. There exist a plurality of mobile stations receiving the multicast data, but the following will describe the operation of only one mobile station out of them. It is a matter of course that like operation is carried out at the other mobile stations being multicast targets omitted to describe.
• At thebase station201, multicast data addressed to themobile stations211, entering thedata input terminal6, is fed into theARQ processor202. TheARQ processor202 stores the multicast data for retransmission in thememory210, thereafter attaches the CRC to the data and performs error-correction code coding thereof, and further attaches information about a number of a base station antenna used for transmission and then outputs the data to thetransmitter3. Then thetransmitter3 controls theantenna switching unit109 so as to implement transmission from the antenna indicated by the information on the number of the base station antenna thus attached. Thetransmitter3 modulates the input multicast data into a transmitted signal (multicast signal) and thereafter outputs the signal to theantenna switching unit109. Theantenna switching unit109 is configured to be able to transmit the multicast signal through the transmitted/receivedwave splitter4 and from the base station antenna corresponding to the aforementioned number information (either the firstbase station antenna7 or the second base station antenna8).
• In the present embodiment, it is assumed that theantenna switching unit109 is controlled so as to be able to transmit the multicast signal, preferentially using a base station antenna with the greatest number of requests from the mobile stations being the multicast targets. Namely, before outputting the multicast data to thetransmitter3, theARQ processor202 searches the information stored in thememory210 for the information on the number of the base station antenna with the greatest number of requests from the mobile stations, and controls theantenna switching unit109 so as to transmit the multicast signal from the base station antenna corresponding to the number. Thememory210 is used for storing correspondences between the numbers of requests from the mobile stations and the numbers of the base station antennas.
• At themobile station211 on the other hand, the multicast signal received at themobile station antenna17 through thedownlink22 is fed through the transmitted/receivedwave splitter16 into thereceiver12. Thereceiver12 demodulates the received multicast signal and outputs the demodulated signal as received multicast data to theARQ processor213. TheARQ processor213 performs the decoding of error correction code and thereafter performs the error detection using the attached CRC. At the same time, theARQ processor213 stores a likelihood obtained in the decoding of error correction code, together with the information on the number of the base station antenna attached to the received multicast data, in thememory119. The foregoing likelihood can be the number of corrected bits in the case of the error-correction code coding being the block code such as the BCH code, the RS code, or the like, or a metric in the case of the convolutional code.
• When the foregoing error detection with the CRC finds no error in the received multicast data, theARQ processor213 outputs the received multicast data from thedata output terminal14, without transmitting any signal to thebase station201 at all. When an error is detected in the received multicast data on the other hand, theARQ processor213 searches the information stored in thememory119 for the information on the number of the base station antenna with the highest receiving quality and outputs the information on the number of the base station antenna together with a repeat request for retransmission of the received multicast data to thetransmitter15. Thetransmitter15 transmits the repeat request of the received multicast data and the information on the number of the base station antenna through theuplink21 to thebase station201.
• At thebase station201, thereceiver5 receives the repeat request of the received multicast data and the information on the number of the base station antenna and thereceiver5 outputs the data to theARQ processor202. TheARQ processor202, as described previously, measures the number of requests for the numbers of the base station antennas requested by the mobile stations, stores the correspondences between the numbers of the base station antennas and the numbers of mobile stations requesting the respective antennas, in thememory210, and, on the occasion of retransmitting the multicast data thereafter, retransmits the data, preferentially using the base station antenna with the greatest number of requests.
• The following will describe the cooperative operation of thebase station201 and a plurality of mobile stations (four mobile stations A to D as an example herein) with reference toFIG. 9. The configuration of the mobile stations A to D is substantially the same as that of themobile station211 shown inFIG. 8, and they are in an initial state in which no data is stored yet in thememory210 provided in thebase station201 and in thememories119 provided in the respective mobile stations.
• Thebase station201 attaches the number information of thefirst antenna7 to multicast data, and transmits the multicast data with the number information thus attached, to all the mobile stations (the mobile stations A to D) as multicast targets. For example, let us suppose the mobile stations A to C detect an error in the received multicast data. Then the mobile stations A to C send to the base station201 a repeat request for retransmission of the data and an antenna use request that thesecond antenna8, an error rate of which is not stored yet in thememory119, should be used. Since the mobile station D detects no error in the received multicast data, it transmits nothing to thebase station201.
• At thebase station201, theARQ processor202 then measures the number of requests for the information on the number of each antenna to be used for retransmission, from the mobile stations A to C, and stores the results of the measurement, i.e., information indicating that the number of requests for retransmission from thesecond antenna8 is three and that the number of requests for retransmission from thefirst antenna7 is zero, in thememory210. For this reason, based on the foregoing results of the measurement stored in thememory210, thebase station201 transmits the multicast data to be retransmitted (hereinafter referred to as retransmitted multicast data) to the mobile stations A to C from thesecond antenna8 with the maximum number of requests for retransmission (this step corresponds to “first retransmission” inFIG. 9).
• In the reception of the first retransmitted multicast data, the mobile stations A to C again detect an error, and then send a repeat request to thebase station201. At the mobile station A, an error rate is lower in the reception of the multicast data transmitted from thesecond antenna8, and the mobile station A sends a use request for use of thesecond antenna8, together with the notification of the repeat request, to thebase station201. On the other hand, at the mobile stations B and C, an error rate is lower in the reception of the multicast data transmitted from thefirst antenna7, and thus they send a use request for use of thefirst antenna7, together with the notification of the repeat request, to thebase station201.
• At thebase station201, theARQ processor202 stores information that the number of requests for retransmission from thesecond antenna8 is one and the number of requests for retransmission from thefirst antenna7 is two, in thememory210. For this reason, based on the results of the above measurement stored in thememory210, thebase station201 transmits the retransmitted multicast data to the mobile stations A to C from thefirst antenna7 with the maximum number of requests for retransmission (this step corresponds to “second retransmission” inFIG. 9).
• The mobile stations B and C detect no error in the reception of the second retransmitted multicast data, and thus they transmit nothing to thebase station201. On the other hand, the mobile station A detects an error, but it sends no repeat request to thebase station201, because the base station antenna used for the transmission is not the antenna requested by the mobile station A. This is because in the next transmission the retransmitted multicast data is expected to be transmitted using thesecond antenna8 requested by the mobile station A.
• Thereafter, based on the results of the measurement stored in thememory210, thebase station201 transmits the retransmitted multicast data to the mobile station A from thesecond antenna8 with the second highest number of requests for retransmission (this step corresponds to “third retransmission” inFIG. 9).
• The mobile station A detects no error in the reception of the third retransmitted multicast data, and thus transmits nothing to thebase station201, thus completing the multicast transmission from thebase station201.
• By the operation as described above, it becomes feasible to implement the transmission of high-quality signals with the automatic repeat request of the present invention in the transmission of multicast data.
• According to the second embodiment described above, thebase station201 transmits the retransmitted multicast data, using the base station antennas in descending order of the number of antenna use requests based on the receiving qualities of signals measured at the respective mobile stations, and it is thus feasible as a whole of the mobile communication system to improve the receiving qualities of retransmitted multicast data at more mobile stations, to decrease the total number of occurrences of repeat requests, and to enhance the total throughput of the entire system.
• The above first and second embodiments described the examples in which the mobile station transmitted the antenna use request for use of one antenna out of the plurality of base station antennas, but it is also possible in the case of a number of base station antennas being provided, to employ a configuration wherein the mobile station transmits an antenna use request designating two or more base station antennas with better receiving qualities, as antennas to be used.
• Incidentally, while the present invention can be mentioned as a so-called diversity system wherein one base station uses plural antennas, site diversity is known as a diversity system wherein a plurality of base stations use one antenna.
• This site diversity has the advantage of great diversity gain because of no correlation with shadowing (variation of local median value), but it has the following disadvantages against the fading (instantaneous variation), though demonstrating some great diversity gain because of no correlation therewith: the delay in control time is too large to realize the satisfactory diversity gain because of transmission of control signals between plural base stations; the efficiency is low, because radio resources and devices for the plural base stations are preliminarily occupied for the control in order to adapt to the instantaneous variation.
• When the present invention is applied in combination with the above site diversity, it can provide the effect of increase in the diversity gain thanks to the use of the plural base stations against the shadowing. Since the control time can be unlimitedly shortened by the feature of the present invention of using plural antennas in one base station, satisfactorily large diversity gain can be realized against the fading. By applying the site diversity to the present invention as described, it is feasible to attain the maximum diversity gain.
• The present embodiment can also be applied to the mobile station functioning as a relay station instead of the base station, supposing the situation of multihop connection. In this case, themobile station211, which is a transmitting station of a repeat request, preliminarily identifies existence of an adjoining mobile station as relay station and requests retransmission of a signal by designating a transmission path including the mobile station (relay station). Similarly, thebase station201, which is a transmitting station of the signal according to the repeat request, preliminarily identifies existence of an adjoining mobile station as a relay station and responds to the repeat request by designating a transmission path including the mobile station (relay station).
Third Embodiment
• The third embodiment of the present invention will be described with reference toFIGS. 10 and 11. The present embodiment will describe an example in which the base station transmits the signal to the mobile station in the multiband transmission system.
• FIG. 10 is a block diagram of the mobile communication system in the present embodiment, which is generally comprised of abase station301 and amobile station311. Thebase station301 comprises anARQ processor302, a transmitter/receiver303, asignal input terminal304, abase station antenna305, and achannel determiner306. Themobile station311 comprises a transmitter/receiver312, anARQ processor313, asignal output terminal314, amobile station antenna315, a receivingquality measuring unit316, and amemory317.
• The following will describe the operation with reference to the flowchart ofFIG. 11.
• At thebase station301, a signal addressed to themobile station311, entering thesignal input terminal304, is fed into theARQ processor302. TheARQ processor302 attaches the error-detectable parity such as the CRC or the like to the signal so as to permit the detection of an error occurring during transmission, thereafter stores the signal for retransmission (T2), and outputs the signal to the transmitter/receiver303. The transmitter/receiver303 informs themobile station311 of a transmission start of the signal addressed to themobile station311 and a number of a frequency channel in a frequency band for transmission of the signal (T3) and thereafter transmits the signal to the mobile station311 (T4).
• If candidates are preliminarily known for the number of the frequency channel in the frequency band for transmission of the signal, it is also possible to omit the informing step of the number of the frequency channel in the frequency band.
• On the other hand, at themobile station311, the receivingquality measuring unit316 continuously, constantly measures C/I (Carrier-to-Interfere ratio: carrier power to interference power ratio) of individual channels transmitted from thebase station301, as receiving qualities (T1), and stores relations between numbers of frequency channels in frequency bands Measured, and C/I's of the frequency channels in thememory317.
• As described above, the receivingquality measuring unit316 continuously, constantly measures the C/I's of individual channels or the like transmitted from thebase station301. Therefore, the relations are always updated between numbers of frequency channels in frequency bands, and C/I's of the frequency channels in thememory317.
• At themobile station311 in this configuration, the signal addressed to the mobile station, transmitted from thebase station301, is received through thedownlink322 by the transmitter/receiver312 (T5), and thereafter the signal is fed into theARQ processor313. TheARQ processor313 performs the error detection of the received signal using the CRC. When no error is detected in the received signal (NO at T6), theARQ processor313 outputs the received signal from thesignal output terminal314 and also sends an acknowledgement of arrival of the received signal through theuplink321 to theARQ processor302 of the base station301 (T7). Then theARQ processor302, receiving the notification of the arrival acknowledgement from each mobile station, deletes the signal addressed to the mobile station, stored for retransmission (T9 and T10). In this respect, it is also possible to employ a configuration without the notification of the arrival acknowledgement (T7), wherein the process of detecting the repeat request (T9) is provided with a time-out judging function and the operation of T10 is carried out when no repeat request is detected within a certain period of time.
• When at T6 an error is detected in the received signal (YES at T6) on the other hand, theARQ processor313 sends a repeat request for retransmission of the received signal through theuplink321 to theARQ processor302 of thebase station301 and also sends to thechannel determiner306 of the base station301 a number of a frequency channel in a frequency band with the maximum C/I out of those measured and stored in thememory317, and the C/I of the frequency channel (T8).
• When theARQ processor302 receives the repeat request, it is determined at T9 whether the input signal is a repeat request. When a repeat request is detected at the determination of T9 (YES at T9), thechannel determiner306 is notified of the result of the detection. Receiving the notification of the detection of the repeat request from theARQ processor302, thechannel determiner306 calculates such a transmission power that the receiving quality at themobile station311 becomes a required value, based on the C/I thus notified of (T11), and then controls the transmitter/receiver303 so that the signal under the repeat request is retransmitted by the frequency channel number notified of and the transmission power calculated. Then the signal retransmitted from theARQ processor302 is fed into the transmitter/receiver303, and the transmitter/receiver303 informs the mobile station of the number of the frequency channel in the frequency band used for retransmission (T12) and thereafter transmits the retransmitted signal thereto (T13).
• Thebase station301 also transmits a new signal addressed to the mobile station, entering thesignal input terminal304 thereafter, by using the number of the frequency channel in the frequency band and the transmission power acquired in the above operation.
• When candidates are known in advance for the number of the frequency channel in the frequency band used for retransmission, the base station omits the informing step of the number of the frequency channel in the frequency band used for retransmission and the mobile station receives the retransmitted signal by the use of the number of the frequency channel in the frequency band with the maximum receiving quality out of the candidates for the number of the frequency channel in the frequency band.
• As described above, the present embodiment showed the example using the multiband transmission system as an example of the transmission system between thebase station301 and themobile station311, and besides, it is also possible to use the FDM (Frequency Division Multiplexing) transmission system, the multicarrier transmission system, or the OFDM (Orthogonal Frequency Division Multiplexing) transmission system as a transmission system between thebase station301 and themobile station311. For example, thebase station301 is notified of a number of a frequency channel and a receiving quality of the frequency channel in the case of the FDM transmission system being used; of a number of a subcarrier channel and a receiving quality of the subcarrier channel in the case of the multicarrier transmission system being used; or of a number of an orthogonal subcarrier channel and a receiving quality of the orthogonal subcarrier channel in the case of the OFDM transmission system being used, whereby the receiving quality at themobile station311 can be improved by the operation similar to that in the present embodiment.
• According to the third embodiment of the present invention, as described above, thebase station301 calculates the transmission power to achieve the required receiving quality at the mobile station, based on the number of the frequency channel and the C/I of the frequency channel notified of by themobile station311, and retransmits the signal under the repeat request from themobile station311, using the number of the frequency channel notified of and the transmission power thus calculated, whereby themobile station311 can be prevented from being kept in the low receiving quality state because of fading or shadowing. As a consequence, the repetition of repeat requests from themobile station311 can be reduced, so as to enhance the throughput. Since the retransmission of the retransmitted signal is carried out after changeover into the frequency channel with the minimum transmission power from thebase station301, interference can be reduced withmobile stations311 not receiving the retransmitted signal.
• The present embodiment can also be applied to the mobile station functioning as a relay station instead of the base station, supposing the situation of multihop connection. In this case, themobile station311, which is a transmitting station of a repeat request, preliminarily identifies existence of an adjoining mobile station as relay station and requests retransmission of a signal by designating a transmission path including the mobile station (relay station). Similarly, thebase station301, which is a transmitting station of the signal according to the repeat request, preliminarily identifies existence of an adjoining mobile station as a relay station and responds to the repeat request by designating a transmission path including the mobile station (relay station).
Fourth Embodiment
• The fourth embodiment of the present invention will be described below with reference to FIGS.12 to15. The present embodiment will describe an example in which the base station transmits a multicast signal to each mobile station in the FDM transmission system.
• FIG. 12 is a block diagram of the mobile communication system in the fourth embodiment, which is generally comprised of abase station401 and amobile station411, as in the third embodiment described above. Thebase station401 comprises anARQ processor402, a transmitter/receiver403, asignal input terminal404, abase station antenna405, and achannel determiner406. Themobile station411 comprises a transmitter/receiver412, anARQ processor413, asignal output terminal414, amobile station antenna415, a receiving quality measuring unit416, and amemory417.
• The following will describe the operation of the mobile communication system in the present embodiment with reference to the flowchart ofFIG. 13. There exist a plurality of mobile stations in a group receiving one multicast signal, but only one mobile station in the group will be described below as a typical example. The other mobile stations belonging to the group also perform the operation similar to that of the mobile station described below.
• At thebase station401, a multicast signal addressed to themobile stations411, entering thesignal input terminal404, is fed into theARQ processor402. TheARQ processor402 attaches the error-detectable parity such as the CRC or the like to the signal so as to permit the detection of an error occurring during transmission, thereafter stores the multicast signal for retransmission (T22), and outputs the signal to the transmitter/receiver403. The transmitter/receiver403 informs each mobile station of a start of transmission of the multicast signal and a number of a frequency channel for transmission of the multicast signal, and thereafter transmits the multicast signal to the mobile station411 (T23 and T24).
• When candidates are known in advance for the number of the frequency channel used for transmission of the multicast signal, it is also possible to omit the informing step of the frequency channel number.
• On the other hand, at themobile station411, the receiving quality measuring unit116 continuously, constantly measures C/I of an individual channel or the like transmitted from thebase station401 as a receiving quality (T21), and stores the relation between the number of the frequency channel and the C/I of the frequency channel thus measured, in the memory117.
• As described above, the receiving quality measuring unit416 continuously, constantly measures the C/I's of the individual channels or the like transmitted from thebase station401. Therefore, the relations are always updated between the numbers of the frequency channels, and the C/I's of the frequency channels in the memory117.
• The present embodiment will be described hereinafter, supposing the receiving quality is C/I. It is, however, also possible to use as the receiving quality a received power, C/(I+N), S/(I+N), C/N, S/N, an error rate, a likelihood obtained in decoding of error correction code, a base station transmission power value, an amount of increase or attenuation of the base station transmission power, or a combination of these. The character “C” in C/(I+N) above represents the carrier power, and “S” in S/(I+N) above the signal power. Further, the character “I” in above C/(I+N) and above S/(I+N) represents the interference power, and “N” the noise power.
• In the present invention, as described, it is possible to use any signal for the measurement of receiving quality as long as it is a signal transmitted from thebase station401 configured to transmit the multicast signal.
• At themobile station411, the multicast signal transmitted from thebase station401 is received through thedownlink422 at the transmitter/receiver412 (T25) and thereafter is fed into theARQ processor413. TheARQ processor413 performs the error detection of the received multicast signal using the CRC. When no error is detected in the received multicast signal (NO at T26), theARQ processor413 outputs the received multicast signal from thesignal output terminal414 and sends an acknowledgement of arrival of the received multicast signal to theARQ processor402 of thebase station401 through the uplink421 (T27).
• TheARQ processor402, receiving only the notification of the arrival acknowledgement from each mobile station, deletes the multicast signal stored for retransmission (NO at T29, and T30). In this respect, it is also possible to employ a configuration without the foregoing notification of the arrival acknowledgement (T27), wherein the process of detecting the repeat request (T29) is provided with a time-out judging function and the operation of (T30) is executed when no repeat request is detected within a certain period of time.
• When an error is detected in the received multicast signal on the other hand (YES at T26), theARQ processor413 sends a repeat request for retransmission of the received multicast signal through theuplink421 to theARQ processor402 of thebase station401. TheARQ processor413 also makes access to thememory417 and notifies thechannel determiner406 of thebase station401, of the latest frequency channel number and the C/I of the frequency channel measured and stored in the memory417 (T28).
• When the repeat request is fed into theARQ processor402, it is determined at (T29) whether the input signal is a repeat request. When a repeat request is detected at the determination of T29 (YES at T29), thechannel determiner406 is notified of the result of the detection. When thechannel determiner406 receives the notification that the repeat request is detected by theARQ processor402, it determines a number of a frequency channel for retransmission and a transmission power of the frequency channel on the basis of the frequency channel number and the C/I of the frequency channel notified of by each mobile station (T31), and thereafter controls the transmitter/receiver403 so as to retransmit the signal by the use of the frequency channel number and the transmission power thus determined.
• Then the multicast signal stored for retransmission at theARQ processor402 is fed into the transmitter/receiver403, and the transmitter/receiver403 informs the mobile station of numbers of frequency channels or a number of a single frequency channel used for retransmission (T32) and thereafter transmits the input retransmitted multicast signal (T33).
• Each mobile station to receive the retransmitted multicast signal, receives the retransmitted multicast signal in a channel of a frequency channel number with the maximum receiving quality at the mobile station out of the frequency numbers thus informed of. When candidates are known in advance for the numbers of the frequency channels or the number of the single frequency channel used for retransmission, the informing step of the frequency channel number for retransmission of the multicast signal is omitted, and each mobile station receives the retransmitted multicast signal in a channel of a frequency channel number with the maximum receiving quality out of the candidates for the frequency channel numbers.
• Thebase station401 can also transmit a new multicast signal entering thesignal input terminal404 in processing thereafter, using the numbers of the frequency channels or the number of the single frequency channel and the transmission power determined above.
• As described above, the fourth embodiment described the case using the FDM transmission system as an example of the transmission system between thebase station401 and themobile station411, and besides, it is also possible to use the multicarrier transmission system, the OFDM transmission system, or the multiband transmission system as a transmission system between thebase station401 and themobile station411. For example, thebase station401 is notified of a number of a subcarrier channel and a receiving quality of the subcarrier channel in the case of the multicarrier transmission system being used; of a number of an orthogonal subcarrier channel and a receiving quality of the orthogonal subcarrier channel in the case of the OFDM transmission system being used; or of a number of a frequency channel in a frequency band and a receiving quality of the frequency channel in the frequency band in the case of the multiband transmission system being used, whereby the receiving quality at themobile station411 can be improved by the operation similar to that of the present embodiment.
• According to the fourth embodiment of the present invention, as described above, thebase station401 determines the frequency channel number for retransmission of the multicast signal and the transmission power of the frequency channel on the basis of the frequency channel number and the C/I of the frequency channel notified of by each mobile station and thereafter retransmits the signal by the frequency channel number and transmission power thus determined. Therefore, themobile station411 can receive the retransmitted multicast signal with the required receiving quality even in a state under the influence of fading or shadowing. As a consequence, the repetition of repeat requests from themobile station411 is reduced, so as to enhance the throughput. The interference can be reduced with mobile stations not receiving the retransmitted multicast signal.
• The following will describe an example of the procedure of determining the number of the frequency channel in the radio channel and the transmission power on the assumption of the mobile communication system in the present embodiment and with reference toFIG. 14.
• The determination of the frequency channel number and the transmission power is done at thechannel determiner406 of the base station.FIG. 14 is a flowchart (algorithm) showing the processing procedure of determining the frequency channel number and the transmission power.FIG. 15 shows an example of receiving qualities of respective frequency channels at each ofmobile stations1 to3.
• For convenience of explanation, the following will describe an example in which the number of frequency channels available is three (f=0, 1, or 2). Since it is possible to select an arbitrary number of frequency channels up to three, there are seven combinations (c=0-6) of frequencies accordingly. The following description will be given on the presumption that thechannel determiner406 is already notified of the receiving qualities of the respective frequency channels at each of the mobile stations. For example, as shown inFIG. 15, thechannel determiner406 is assumed to be notified of the receiving qualities at the respective mobile stations1-3.
• FIG. 15 is a graph showing an example in which each mobile station1-3 is monitoring the receiving qualities of signals of the first to third frequency channels transmitted from thebase station401, as described previously. InFIG. 15, the horizontal axis represents the frequency (f) and the vertical axis the receiving quality (dB). As shown inFIG. 15, for example, themobile station1 is in a state in which the receiving quality of the first frequency channel (f=0) is 0 dB, the receiving quality of the second frequency channel (f=1) −1 dB, and the receiving quality of the third frequency channel (f=2) −15 dB.
• Similarly, themobile station2 is in a state in which the receiving quality of the first frequency channel (f=0) is −20 dB, the receiving quality of the second frequency channel (f=1) 0 dB, and the receiving quality of the third frequency channel (f=2) −10 dB. Themobile station3 is in a state in which the receiving quality of the first frequency channel (f=0) is −15 dB, the receiving quality of the second frequency channel (f=1) −20 dB, and the receiving quality of the third frequency channel (f=2) 0 dB. In the present example, the required receiving quality (Qreq) at each mobile station1-3 is assumed to be 0 dB.
• As a premise of describing the flowchart ofFIG. 14 herein, the following presents correspondence relations between the combinations of frequency channels f assumed to be used for retransmission, and c representing classes of the combinations.
• c=0: f=0 (the first frequency channel being used)
• c=1: f=1 (the second frequency channel being used)
• c=2: f=2 (the third frequency channel being used)
• c=3: f=0, 1 (the first and second frequency channels being used)
• c=4: f=1, 2 (the second and third frequency channels being used)
• c=5: f=0, 2 (the first and third frequency channels being used)
• c=6: f=0, 1, 2 (the first, second, and third frequency channels being used)
• InFIG. 14, the first step is to assume c=0, i.e., that only the first frequency channel is used, and set the mobile station1 (i=0) as a mobile station (T41). Then calculation of (T42) is executed. At T42, MAX{q(i,f)} is calculated. Here q(i,f) indicates the receiving quality of the frequency channel f at the mobile station i. Further, MAX{q(i,f)} indicates maximum q(i,f) among all the frequency channels f in the combination class c of the frequency channels at the mobile station i. In the present example, at i=0, the maximum receiving frequency in the case of c=0 is given at f=0, and thus the calculation is done as follows:
  Q(0,0)=q(0,0)=0 dB
  (reference is made to1 in a circle inFIG. 15).
• After q(0,0) is acquired in this way, the flow proceeds to next (T43) to increment i by “1” (i=1, the mobile station2). At this (T43), the modulo arithmetic is carried out, and thus i is incremented until a remainder in division of (i+1) by M (the number of all mobile stations sending a request) becomes zero. Therefore, 1 mod 3(=M) at this point, which results in i≠0. Thus the determination at T44 is NO, so that the processing from T42 is carried out again. This means that the processing of T42 to T43 is repeatedly carried out until i becomes equal to M (before i=3).
• Accordingly, since the determination at T44 is NO, the flow returns to T42 to execute the calculation of MAX{q(i,f)} for the mobile station2 (i=1). Then the result below is obtained (reference is made to2 in a circle inFIG. 15).
  Q(1,0)=MAX{q(1,0)}=−20 dB
  Further, the calculation for i=2 (mobile station3) is also carried out in much the same manner as the above procedure, and the following result is obtained.
  Q(2,0)=MAX{q(2,0)}=−15 dB
  (reference is made to3 in a circle inFIG. 15).
• After T42 is executed in this way (c=0) for all the mobile stations (i=0-2), the determination at T44 results in i=0 (YES at T44), and then the flow proceeds to next T45.
• At this T45, P(c)=Σ{Qreq−MIN(Q(i,f))} is calculated as follows. In this equation, Qreq represents the required receiving quality, and P(c) the transmission power from the base station in the case of the combination class of frequency channels being c.
• In the case of c=0, the calculation is carried out as follows.$\begin{array}{c}P\left(0\right)=\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(0,0\right),Q\left(1,0\right),Q\left(2,0\right)\right\}\\ =0\mathrm{dB}-\mathrm{MIN}\left\{0\mathrm{dB},-20\mathrm{dB},-15\mathrm{dB}\right\}\\ =0\mathrm{dB}-\left(-20\mathrm{dB}\right)\\ =+20\mathrm{dB}\end{array}$
• Accordingly, for c=0, the calculation results in P(0)=+20 dB.
• After completion of the calculation of P(c) in the case of c=0 in this way, the flow proceeds to next T46 to increment the combination class c of frequency channels. At this point, c becomes 1 mod 6 (Nc) and thus c≠0, leading to NO as the result of the determination at (T47). Thus the processing from (T42) is executed again. Namely, the processing of T42 to T46 is repeatedly carried out until c becomes equal to Nc (before c=6 in the present example).
• The following presents the results of the calculations of Q(i,f) and P(c) executed in much the same manner as the above-stated procedure, for c=1 to c=6.
• In the case of c=1)
  Q(0,1)=MAX{q(0,1)}=−1 dB (cf.4 in a circle in FIG.15)
  Q(1,1)=MAX{q(1,1)}=0 dB (cf.5 in a circle in FIG.15)
  Q(2,1)=MAX{q(2,1)}=−20 dB (cf.6 in a circle in FIG.15)$\begin{array}{c}P\left(1\right)=\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(0,1\right),Q\left(1,1\right),Q\left(2,1\right)\right\}\\ =0\mathrm{dB}-\mathrm{MIN}\left\{-1\mathrm{dB},0\mathrm{dB},-20\mathrm{dB}\right\}\\ =0\mathrm{dB}-\left(-20\mathrm{dB}\right)\\ =+20\mathrm{dB}\end{array}$
• In the case of c=2)
  Q(0,2)=MAX{q(0,2)}=−15 dB (cf.7 in a circle in FIG.15)
  Q(1,2)=MAX{q(1,2)}=−10 dB (cf.8 in a circle in FIG.15)
  Q(2,2)=MAX{q(2,2)} 0 dB (cf.9 in a circle in FIG.15)$\begin{array}{c}P\left(2\right)=\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(0,2\right),Q\left(1,2\right),Q\left(2,2\right)\right\}\\ =0\mathrm{dB}-\mathrm{MIN}\{-15\mathrm{dB},-10\mathrm{dB},0\mathrm{dB}\}\\ =0\mathrm{dB}-\left(-15\mathrm{dB}\right)\\ =+15\mathrm{dB}\end{array}$
• In the case of c=3)
  Q(0,0)=MAX{q(0,0),q(0,1)}=q(0,0)=0 dB
  Q(1,0)=MAX{q(1,0),q(1,1)}=q(1,1)=0 dB
  Q(2,0)=MAX{q(2,0),q(2,1)}=q(2,0)=−15 dB$\begin{array}{c}P\left(3\right)=\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(0,0\right),Q\left(2,0\right)\right\}+\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(1,1\right)\right\}\\ =0\mathrm{dB}-\mathrm{MIN}\left\{0\mathrm{dB},-15\mathrm{dB}\right\}+0\mathrm{dB}-\mathrm{MIN}\left(0\mathrm{dB}\right)\\ =\left(+15\mathrm{dB}\right)+\left(0\mathrm{dB}\right)\\ \approx +15.1\mathrm{dB}\end{array}$
• The above sum of (+15 dB) and (0 dB) is given by a logarithm of the sum of antilogarithms of (+15 dB) and (0 dB).
• The antilogarithm of (0 dB) is “1” and the antilogarithm of (+15 dB) is “≈31.6.” Thus the sum x of these is given as follows.
  x=1+31.6=32.6
  ♭ 10 logx=10 log 32.6≈+15.1 dB.
• In the case of c=4)
  Q(0,1)=MAX{q(0,1),q(0,2)}=q(0,1)=−1 dB
  Q(1,1)=MAX{q(1,1),q(1,2)}=q(1,1)=0 dB
  Q(2,2)=MAX{q(2,1),q(2,2)}=q(2,2)=0 dB$\begin{array}{c}P\left(4\right)=\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(0,1\right),Q\left(1,1\right)\right\}+\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(2,2\right)\right\}\\ =0\mathrm{dB}-\mathrm{MIN}\left\{-1\mathrm{dB},0\mathrm{dB}\right\}+0\mathrm{dB}-\mathrm{MIN}\left(0\mathrm{dB}\right)\\ =\left(+1\mathrm{dB}\right)+\left(0\mathrm{dB}\right)\\ \approx +3.5\mathrm{dB}\end{array}$
• Just as in the above case, the sum of (+1 dB) and (0 dB) is given by a logarithm of the sum of antilogarithms of (+1 dB) and (0 dB).
• The antilogarithm of (0 dB) is “1” and the antilogarithm of (+1 dB) is “≈1.26.” Thus the sum x of these is given as follows.
  x=1+1.26=2.26
  ♭ 10 logx=10 log 2.26≈+3.5 dB.
• In the case of c=5)
  Q(0,0)=MAX{q(0,0),q(0,2)}=q(0,0)=0 dB
  Q(1,2)=MAX{q(1,0),q(1,2)}=q(1,2)=−10 dB
  Q(2,2)=MAX{q(2,0),q(2,2)}=q(2,2)=0 dB$\begin{array}{c}P\left(5\right)=\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(0,0\right)\right\}+\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(1,2\right),Q\left(2,2\right)\right\}\\ =0\mathrm{dB}-\mathrm{MIN}\left(0\mathrm{dB}\right)+0\mathrm{dB}-\mathrm{MIN}\left\{-10\mathrm{dB},0\mathrm{dB}\right\}\\ =\left(0\mathrm{dB}\right)+\left(+10\mathrm{dB}\right)\\ \approx +10.4\mathrm{dB}\end{array}$
• Just as in the above case, the sum of (0 dB) and (+10 dB) is given by a logarithm of the sum of antilogarithms of (0 dB) and (+10 dB).
• The antilogarithm of (0 dB) is “1” and the antilogarithm of (+10 dB) is “10.1” Thus the sum x of these is given as follows.
  x=1+10=11
  ♭ 10 logx=10log 11≈10.4 dB.
• In the case of c=6)
  Q(0,0)=MAX{q(0,0),q(0,1),q(0,2)}=q(0,0)=0 dB
  Q(1,1)=MAX{q(1,0),q(1,1),q(1, 2)}=q(1,1)=0 dB
  Q(2,2)=MAX{q(2,0),q(2,1),q(2,2)}=q(2,2)=0 dB$\begin{array}{c}P\left(6\right)=\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(0,0\right)\right\}+\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(1,1\right)\right\}+\mathrm{Qreq}-\mathrm{MIN}\left\{Q\left(2,2\right)\right\}\\ =0\mathrm{dB}-\mathrm{MIN}\left(0\mathrm{dB}\right)+0\mathrm{dB}-\mathrm{MIN}\left(0\mathrm{dB}\right)+0\mathrm{dB}-\mathrm{MIN}\left(0\mathrm{dB}\right)\\ =\left(0\mathrm{dB}\right)+\left(0\mathrm{dB}\right)+\left(0\mathrm{dB}\right)\\ \approx +4.8\mathrm{dB}\end{array}$
• Just as in the above case, the sum of (0 dB), (0 dB), and (0 dB) is given by a logarithm of the sum of antilogarithms of (0 dB), (0 dB), and (0 dB).
• Since the antilogarithm of (0 dB) is “1,” the sum x is given as follows.
  x=1+1+1=3
  ♭ 10 logx=10log 3≈+4.8 dB.
• After completion of the calculations of P(0) to P(6) as described above, the flow proceeds to T48 to calculate MIN{P(c)}.
• The following presents the calculation method of MIN{P(c)}.$\begin{array}{c}\mathrm{MIN}\left\{P\left(c\right)\right\}=\mathrm{MIN}\left\{P\left(0\right),P\left(1\right),P\left(2\right),P\left(3\right),P\left(4\right),P\left(5\right),P\left(6\right)\right\}\\ =\mathrm{MIN}\left\{+20\mathrm{dB},+20\mathrm{dB},+15\mathrm{dB},+15.1\mathrm{dB},+3.5\mathrm{dB},+10.4\mathrm{dB},+4.8\mathrm{dB}\right\}\end{array}$
  Accordingly, the calculation at T48 obtains the following.
  MIN{P(c)}=P(4)=+3.5 dB.
• The above processing results in finally selecting the combination of frequency channels in c=4. Therefore, while the second frequency channel is set at the transmission power of +1 dB and the third frequency channel at the transmission power of 0 dB, the same multicast signal is retransmitted at each of the frequencies (the second and third frequencies).
• As described above, the above processing permits the frequency channel number(s) minimizing the transmission power from the base station, and the transmission power(s) thereof to be determined while satisfying the required receiving quality at the mobile stations.
• The present embodiment can also be applied to the mobile station functioning as a relay station instead of the base station, supposing the situation of multihop connection. In this case, themobile station411, which is a transmitting station of a repeat request, preliminarily identifies existence of an adjoining mobile station as relay station and requests retransmission of a signal by designating a transmission path including the mobile station (relay station). Similarly, thebase station401, which is a transmitting station of the signal according to the repeat request, preliminarily identifies existence of an adjoining mobile station as a relay station and responds to the repeat request by designating a transmission path including the mobile station (relay station).
Fifth Embodiment
• Lastly, the fifth embodiment of the present invention will be described with reference to the block diagram ofFIG. 16. The present embodiment employs the NACK base automatic repeat request not to send an arrival acknowledgement but to send only a repeat request, and the base station is configured to receive multicast signals of packet units and send them in the multicarrier transmission system. The following will describe an example of combination with a method using spreading codes for repeat requests and thereby permitting detection of repeat requests and numbers of packets under the repeat request even with occurrence of collision between repeat request signals at the base station.
• The method capable of detecting the repeat requests even with occurrence of collision between repeat requests is disclosed in International Patent Application (PCT/JP01/02923).
• FIG. 16 is a block diagram of the mobile communication system in the present embodiment, which is generally comprised of abase station501 and amobile station511, as in the first embodiment and the second embodiment described above. Thebase station501 comprises anARQ processor502, a transmitter/receiver503, asignal input terminal504, abase station antenna505, achannel determiner506, and a repeat request signalquality measuring unit507. Themobile station511 comprises a transmitter/receiver512, anARQ processor513, asignal output terminal514, amobile station antenna515, a receivingquality measuring unit516, and amemory517.
• At thebase station501, packets of a multicast signal entering thesignal input terminal504 are fed into theARQ processor502. TheARQ processor502 attaches the CRC to the input packets and outputs them to the transmitter/receiver503. The transmitter/receiver503 informs each mobile station of a start of transmission of the packets and a number of a subcarrier used for the transmission of the packets and thereafter transmits the packets through thedownlink522 to themobile station511.
• On the other hand, at themobile station511, the receivingquality measuring unit516 continuously, constantly measures as the receiving quality, S/(N+I) of each subcarrier transmitted from thebase station501 and stores the correlation between the subcarrier number and S/(N+I) of the subcarrier thus measured, in thememory517.
• At themobile station511 in this configuration, the packets transmitted from thebase station501 are received through thedownlink522 by the transmitter/receiver512 and thereafter are outputted to theARQ processor513. TheARQ processor513 performs the error detection of the received packets using the CRC. When no error is detected in the received packets, theARQ processor513 outputs the packets from thesignal output terminal514. Since the NACK base automatic repeat request is employed, no arrival acknowledgement is sent to thebase station501 when no error is detected.
• When an error is detected in the received packets, theARQ processor513 notifies thebase station501 through theuplink521 of a repeat request for retransmission of a requested packet and the subcarrier number with the maximum receiving quality stored in thememory517. The present embodiment will describe an example of a method of selecting a channel number with a receiving quality within a certain range as a subcarrier number with the maximum receiving quality at each mobile station and notifying the base station of only the subcarrier thereafter. Spreading codes are used for packet numbers under repeat requests and numbers of subcarriers used for transmission of retransmitted packets. For example, in the case where 256 spreading codes are available, 128 spreading codes can be allocated to identification of packet numbers, and 128 spreading codes to identification of subcarrier numbers. Namely, in this case, a number of a spreading code transmitted from themobile station511 to thebase station501 can be determined by the following calculation.
  Number of spreading code=(packet number)+(subcarrier number)×16
• For example, in the case where the retransmitted packet number is “8” and the subcarrier number for the repeat request of the retransmitted packet is “3,” 8+3×16=56, and thus the mobile station transmits the fifty sixth spreading code as a repeat request signal. This makes a judgment on a repeat request feasible using a correlation value by the spreading code or a level of a signal obtained by the despreading operation as a receiving quality even if collision occurs between repeat request signals at thebase station501. Accordingly, thebase station501 can detect the repeat request for retransmission of the eighth packet through the use of the third subcarrier.
• For the spreading code transmitted from themobile station511, the repeat request signalquality measuring unit507 of thebase station501 detects the retransmitted packet number and subcarrier number. The repeat request signalquality measuring unit507 notifies theARQ processor502 of the retransmitted packet signal detected and notifies thechannel determiner506 of the subcarrier number requested to use in retransmission. Then theARQ processor502 searches for a packet number with the largest number of repeat requests and thereafter controls the transmitter/receiver503 so as to retransmit the packet by the subcarrier number thus searched for. The transmitter/receiver503 informs the mobile station of the retransmission using the subcarrier number and thereafter transmits the retransmitted packet fed from theARQ processor502, using the subcarrier.
• As described above, the receiving quality at the mobile station can be improved by the configuration and operation of the mobile communication system in the present embodiment.
• According to the mobile communication system in the present embodiment, thebase station501 receives from themobile station511 the repeat request signal assigned by the spreading code and thus, even with occurrence of collision between repeat request signals at thebase station501, thebase station501 can detect each repeat request for retransmission of which packet using which subcarrier, by determining the correlation value of the spreading code. Since the packet with the greatest number of repeat requests is retransmitted using the subcarrier with the greatest number of requests (the subcarrier with the maximum receiving quality), the mobile station can receive the packet with the required receiving quality under the repeat request. As a consequence, the repetition of repeat requests from the mobile station can be reduced, so as to enhance the throughput.
• The present embodiment can also be applied to the mobile station functioning as a relay station instead of the base station, supposing the situation of multihop connection. In this case, themobile station511, which is a transmitting station of a repeat request, preliminarily identifies existence of an adjoining mobile station as relay station and requests retransmission of a signal by designating a transmission path including the mobile station (relay station). Similarly, thebase station501, which is a transmitting station of the signal according to the repeat request, preliminarily identifies existence of an adjoining mobile station as a relay station and responds to the repeat request by designating a transmission path including the mobile station (relay station).
• In each of the above embodiments, the receiving quality measuring function of the receivingquality measuring unit316,416,516 in themobile station311,411,511 corresponds to the receiving quality measuring means, and the receiving quality transmitting function of the transmitter/receiver312,412,512 to the receiving quality notifying means.
• The transmitting function of the transmitter/receiver303,403,503 in thebase station301,401,501 corresponds to the transmitting means; the channel determining function of thechannel determiner306,406,506 corresponds to the radio channel determining means and to the first, second, and third channel number determining means. Further, the transmission power calculating function of thechannel determiner306,406,506 corresponds to the first and second radio channel transmission power determining means.
• From the invention thus described, it will be obvious that the embodiments of the invention may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, and all such modifications as would be obvious to one skilled in the art are intended for inclusion within the scope of the following claims.

Claims (49)

1. A mobile station configured to perform signal transmission/reception control including signal retransmission control based on an automatic repeat request, with a base station equipped with a plurality of antennas and configured to transmit a signal on the basis of a signal transmission request from at least one antenna out of the plurality of antennas, said mobile station comprising:

a quality measuring unit configured to measure receiving qualities of signals transmitted from the plurality of antennas of said base station; and

a transmitter configured to transmit an antenna use request to said base station that a signal should be transmitted from at least one antenna out of said plurality of antennas, based on the receiving qualities of the signals from the respective antennas obtained by measurement.

2. A mobile station configured to perform signal transmission/reception control including multicast signal retransmission control based on an automatic repeat request, with a base station equipped with a plurality of antennas and configured to transmit a multicast signal on the basis of a signal transmission request from at least one antenna out of the plurality of antennas, said mobile station comprising:

a quality measuring unit configured to measure receiving qualities of signals transmitted from the plurality of antennas of said base station; and

a transmitter configured to transmit an antenna use request to said base station that a multicast signal should be transmitted from at least one antenna out of said plurality of antennas, based on the receiving qualities of the signals from the respective antennas obtained by measurement.

3. The mobile station according toclaim 1, wherein said quality measuring unit measures said receiving quality by using a synchronization signal, a signal of annunciation information, an individual signal to the mobile station, a multicast signal, or a combination of two or more out of these signals, transmitted from at least one antenna of said base station.

4. The mobile station according toclaim 1, wherein said receiving quality is a received power, a value obtained by dividing a carrier power by the sum of an interference power and a noise power, a value obtained by dividing a signal power by the sum of an interference power and a noise power, an error rate, a likelihood obtained in decoding of error correction code, a C/N ratio, an S/N ratio, a correlation value obtained by despreading of spreading code, or a combination of two or more out of these.

5. A signal transmitting method in a mobile communication system comprising a mobile station and a base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request, said signal transmitting method being carried out as follows in the mobile communication system:

measuring at said mobile station a receiving quality of a radio signal transmitted from the base station,

notifying at said mobile station the base station of the receiving quality of the radio signal thus measured, and

transmitting from said base station a signal under a repeat request from said mobile station so as to meet a required receiving quality of the mobile station, based on the receiving quality thus notified of,

wherein when a repeat request for retransmission of a received signal is needed, said mobile station notifies said base station of said repeat request, together with said receiving quality of the radio signal measured.

6. The signal transmitting method according toclaim 5, wherein the radio signal transmitted from said base station becomes at least one radio channel.

7. The signal transmitting method according toclaim 6, wherein said mobile station uses, as a radio channel for measurement of the receiving quality, an annunciation information channel or an individual channel or a multicast channel or a combination of these, among said at least one radio channel transmitted from said base station.

8. The signal transmitting method according toclaim 7, wherein said receiving quality is one selected from at least one of the following:

a received power;

C/(I+N)  (Eq. 1)

C: carrier power

I: interference power

N: noise power;

S/(I+N)  (Eq. 2)

S: signal power

I: interference power

N: noise power;

C/N  (Eq. 3)

C: carrier power

N: noise power;

S/N  (Eq. 4)

S: signal power

N: noise power;

an error rate;

a likelihood obtained in decoding of error correction code;

a transmission power value of the base station;

an increase amount or an attenuation amount of the transmission power of the base station.

9. The signal transmitting method according toclaim 6, wherein radio channels transmitted and received between said base station and said mobile station are at least one of subcarrier channels, orthogonal subcarrier channels, frequency channels, and frequency channels in different frequency bands.

10. The signal transmitting method according toclaim 5, wherein on an occasion of notifying said base station of an acknowledgement of arrival of a received signal, said mobile station notifies the base station of the receiving quality of said at least one radio channel measured.

11. The signal transmitting method according toclaim 5, wherein said mobile station notifies the base station of a number of at least one radio channel and a receiving quality of the radio channel, or of only a channel number of a receiving quality within a predetermined range, as the receiving quality of said at least one radio channel measured.

12. The signal transmitting method according toclaim 5, wherein said mobile station notifies said base station of a number of at least one radio channel satisfying a required receiving quality, including a radio channel with a maximum receiving quality at said mobile station, together with the receiving quality achieved.

13. The signal transmitting method according toclaim 5, wherein said base station determines a radio channel satisfying the required receiving quality at the mobile station on the basis of notification from said mobile station, and

the base station transmits a signal under a repeat request from the mobile station, using the radio channel determined.

14. The signal transmitting method according toclaim 13, wherein after transmitting the signal under the repeat request from said mobile station, using said determined radio channel, said base station also transmits a signal addressed to the mobile station, using said determined radio channel.

15. The signal transmitting method according toclaim 13, wherein, based on the notification from said mobile station, said base station determines a number of a radio channel which satisfies the required receiving quality at the mobile station and through which the signal is transmitted so that a transmission power from the base station becomes a predetermined value, and also determines a transmission power of the radio channel.

16. The signal transmitting method according toclaim 15, wherein when said base station transmits an identical multicast signal to a plurality of mobile stations, the base station determines a number of at least one radio channel which satisfies the required receiving quality at each mobile station and through which the multicast signal is transmitted so that a transmission power from the base station becomes a predetermined value, and also determines a transmission power of the radio channel, based on notification from each mobile station.

17. The signal transmitting method according toclaim 16, wherein when said base station transmits the identical multicast signal to the plurality of mobile stations, the base station determines a number of a radio channel that can be assumed to have the greatest number of repeat requests from the mobile stations, out of channel numbers with receiving qualities within a predetermined range, notified of by the respective mobile stations.

18. A mobile communication system comprising:

a mobile station, and

a base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request,

wherein said mobile station comprises: a quality measuring unit configured to measure a receiving quality of a radio signal transmitted from the base station; and

a notifying unit configured to notify the base station of the receiving quality of the radio signal thus measured, wherein when a repeat request for retransmission of a received signal is needed, said notifying unit notifies said base station of said repeat request, together with said receiving quality of the radio signal measured, and

said base station comprises: a transmitter configured to transmit a signal under a repeat request from said mobile station so that a required receiving quality is satisfied at the mobile station, based on the receiving quality notified of by the mobile station.

19. The mobile communication system according toclaim 18, wherein said quality measuring unit measures a receiving quality of at least one radio channel transmitted from the base station.

20. The mobile communication system according toclaim 19, wherein said quality measuring unit uses, as a radio channel for measurement of the receiving quality at said mobile station, one selected from an annunciation information channel, an individual channel, a multicast channel, and a combination of these, among said at least one radio channel transmitted from the base station.

21. The mobile communication system according toclaim 19, wherein said receiving quality is one selected from at least one of the following:

a received power;

C/(I+N)  (Eq. 1)

C: carrier power

I: interference power

N: noise power;

S/(I+N)  (Eq. 2)

S: signal power

I: interference power

N: noise power;

C/N  (Eq. 3)

C: carrier power

N: noise power;

S/N  (Eq. 4)

S: signal power

N: noise power;

an error rate;

a likelihood obtained in decoding of error correction code;

a transmission power value of the base station; and

an increase amount or an attenuation amount of the transmission power of the base station.

22. The mobile communication system according toclaim 19, wherein radio channels transmitted and received between said base station and said mobile station are at least one of subcarrier channels, orthogonal subcarrier channels, frequency channels, and frequency channels in different frequency bands.

23. The mobile communication system according toclaim 18, wherein on an occasion of notifying said base station of an acknowledgement of arrival of a received signal, said notifying unit notifies the base station of the receiving quality of said at least one radio channel measured.

24. The mobile communication system according toclaim 18, wherein said notifying unit notifies the base station of a number of at least one radio channel and a receiving quality of the radio channel, or of only a channel number of a receiving quality within a predetermined range, as the receiving quality of said at least one radio channel measured.

25. The mobile communication system according toclaim 18, wherein said notifying unit notifies said base station of a number of at least one radio channel satisfying a required receiving quality, including a radio channel with a maximum receiving quality at said mobile station, together with the receiving quality achieved.

26. The mobile communication system according toclaim 18, wherein said base station comprises:

radio channel determining unit configured to determine a radio channel satisfying the required receiving quality at the mobile station on the basis of notification from said mobile station; and

a transmitter configured to transmit a signal under a repeat request from the mobile station, using the radio channel determined by the radio channel determining unit.

27. The mobile communication system according toclaim 26, wherein after transmitting the signal under the repeat request from said mobile station, using said determined radio channel, said transmitter in said base station also transmits a signal addressed to the mobile station, using said determined radio channel.

28. The mobile communication system according toclaim 26, wherein said base station comprises: first radio channel number unit configured to determine a number of a radio channel which satisfies the required receiving quality at the mobile station and through which the signal is transmitted so that a transmission power from the base station becomes a predetermined value, based on the notification from said mobile station; and first radio channel transmission power determining unit configured to determine a transmission power of the radio channel.

29. The mobile communication system according toclaim 28, wherein said base station comprises:

second radio channel number determining unit configured to, on an occasion of transmitting an identical multicast signal to a plurality of mobile stations, determine a number of at least one radio channel which satisfies the required receiving quality at each mobile station and through which the multicast signal is transmitted so that a transmission power from the base station becomes a predetermined value, based on notification from each mobile station; and

second radio channel transmission power determining unit configured to determine a transmission power of the radio channel.

30. The mobile communication system according toclaim 29, wherein said base station comprises:

third radio channel number determining unit configured to, on an occasion of transmitting the identical multicast signal to the plurality of mobile stations, determine a number of a radio channel that can be assumed to have the greatest number of repeat requests from the mobile stations, out of channel numbers with receiving qualities within a predetermined range, notified of by the respective mobile stations.

31. The mobile communication system according toclaim 18, wherein said base station comprises:

a radio resource determining unit configured to determine a radio resource satisfying the required receiving quality at the mobile station on the basis of notification from said mobile station; and

a transmitter configured to transmit the signal under the repeat request from said mobile station, using the radio resource determined by said radio resource determining unit.

32. The mobile communication system according toclaim 18, wherein said transmitter of said base station transmits the signal by using radio resources in decreasing order of the number of repeat requests from the mobile station.

33. The mobile communication system according toclaim 31, wherein said radio resource is at least one antenna, directivities of at least one antenna, a radio channel, a transmission path, or either of combinations of these.

34. A base station in a mobile communication system comprising a mobile station and the base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request, said base station comprising:

a transmitter configured to transmit a signal under a repeat request from said mobile station so that a required receiving quality is satisfied at the mobile station, based on a receiving quality notified of by the mobile station wherein said receiver quality is included in the repeat request.

35. The base station according toclaim 34, said base station comprising:

radio channel determining unit configured to determine a radio channel satisfying the required receiving quality at the mobile station, based on notification from said mobile station; and

said transmitter configured to transmit the signal under the repeat request from the mobile station, using the radio channel determined by the radio channel determining unit.

36. The base station according toclaim 34, wherein after transmitting the signal under the repeat request from said mobile station, using said determined radio channel, said transmitter also transmits a signal addressed to the mobile station, using said determined radio channel.

37. The base station according toclaim 34,

said base station comprising:

first radio channel number determining unit configured to determine a number of a radio channel which satisfies the required receiving quality at the mobile station and through which the signal is transmitted so that a transmission power from the base station becomes a predetermined value, based on notification from said mobile station; and

first radio channel transmission power determining means for determining a transmission power of the radio channel.

38. The base station according toclaim 34,

said base station comprising:

second radio channel number determining unit configured to, on an occasion of transmitting an identical multicast signal to a plurality of mobile stations, determine a number of at least one radio channel which satisfies the required receiving quality at each mobile station and through which the multicast signal is transmitted so that a transmission power from the base station becomes a predetermined value, based on notification from each mobile station; and second radio channel transmission power determining unit for determining a transmission power of the radio channel.

39. The base station according toclaim 34,

said base station comprising:

third radio channel number determining unit configured to, on an occasion of transmitting an identical multicast signal to a plurality of mobile stations, determine a number of a radio channel that can be assumed to have the greatest number of repeat requests from the mobile stations, out of channel numbers with receiving qualities within a predetermined range, notified of by the respective mobile stations.

40. The base station according toclaim 34, wherein radio channels used between said base station and said mobile station are at least one of subcarrier channels, orthogonal subcarrier channels, frequency channels, and frequency channels in different frequency bands.

41. A mobile station in a mobile communication system comprising the mobile station and a base station and configured to perform transmission/reception of a signal while sending and receiving an automatic repeat request,

said mobile station comprising:

a quality measuring unit configured to measure a receiving quality of a radio signal transmitted from the base station; and

a notifying unit configured to transmit a repeat request together with the receiving quality of the radio signal thus measured to the base station.

42. The mobile station according toclaim 41, wherein said quality measuring unit measures a receiving quality of at least one radio channel transmitted from the base station.

43. The mobile station according toclaim 41, wherein said quality measuring unit uses, as a radio channel for measurement of the receiving quality at said mobile station, one selected from an annunciation information channel, an individual channel, a multicast channel, and a combination of these, among said at least one radio channel transmitted from the base station.

44. The mobile station according toclaim 41, wherein said receiving quality is one selected from at least one of the following:

a received power;

C/(I+N)  (Eq. 1)

C: carrier power

I: interference power

N: noise power;

S/(I+N)  (Eq. 2)

S: signal power

I: interference power

N: noise power;

C/N  (Eq. 3)

C: carrier power

N: noise power;

S/N  (Eq. 4)

S: signal power

N: noise power;

an error rate;

a likelihood obtained in decoding of error correction code;

a transmission power value of the base station; and

an increase amount or an attenuation amount of the transmission power of the base station.

45. The mobile station according toclaim 41, wherein when a repeat request for retransmission of a received signal is needed, said notifying unit notifies said base station of said repeat request, together with said receiving quality of the radio signal measured.

46. The mobile station according toclaim 41, wherein on an occasion of notifying said base station of an acknowledgement of arrival of a received signal, said notifying unit notifies the base station of the receiving quality of said at least one radio channel measured.

47. The mobile station according toclaim 41, wherein said notifying unit notifies the base station of a number of at least one radio channel and a receiving quality of the radio channel, or of only a channel number of a receiving quality within a predetermined range, as the receiving quality of said at least one radio channel measured.

48. The mobile station according toclaim 41, wherein said notifying unit notifies said base station of a number of at least one radio channel satisfying a required receiving quality, including a radio channel with a maximum receiving quality at said mobile station, together with the receiving quality achieved.

49. The mobile station according toclaim 41, wherein radio channels used between said mobile station and said base station are at least one of subcarrier channels, orthogonal subcarrier channels, frequency channels, and frequency channels in different frequency bands.

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