S&F Ref: 937890D2 AUSTRALIA PATENTS ACT 1990 COMPLETE SPECIFICATION FOR A STANDARD PATENT Name and Address Fujitsu Limited, of 1-1, Kamikodanaka 4-chome of Applicant: Nakahara-ku, Kawasaki-shi, Kanagawa, 2118588, Japan Actual Inventor(s): Yoshinori Tanaka Yoshihiro Kawasaki Address for Service: Spruson & Ferguson St Martins Tower Level 35 31 Market Street Sydney NSW 2000 (CCN 3710000177) Invention Title: Transmitting apparatus, receiving apparatus and communication method The following statement is a full description of this invention, including the best method of performing it known to me/us: 5845c(6094535_1) TRANSMITTING APPARATUS, RECEIVING APPARATUS AND COMMUNICATION METHOD Technical Field 5 The present invention is related to a transmitting apparatus, receiving apparatus, and communication method, and more particularly to a transmitting apparatus capable of performing data transmission and reception using a plurality of frequencies, a receiving apparatus, and a 10 communication method. Background Art At present, in the field of mobile communication systems, communication systems in operation employ CDMA 15 (Code Division Multiple Access) as a multiple access scheme. On the other hand, a study on next generation mobile communication systems has been very active, aiming for much faster wireless communications. The 3GPP (3rd Generation Partnership Project) which develops standards 20 for third generation mobile communication systems, for example, is working on standardization of new specifications for mobile communication systems, called LTE (Long Term Evolution) (for example, refer to non Patent Literature 1). 25 The next generation mobile communication systems are supposed to employ OFDMA (Orthogonal Frequency Division Multiple Access) or SC-FDMA (Single Carrier 6072332-1 -2 Frequency Division Multiple Access) as a multiple access scheme. 'Such mobile communication systems schedule uplink data transmission from a mobile station to a base station as follows. 5 When the mobile station has control information and other data to transmit, the base station performs dynamic allocation of radio resources in both the frequency domain and the time domain for an uplink data channel. Then, the base station provides the mobile station with the result 10 of the radio resource allocation. According to the result, the mobile station transmits both the control information and the other data at the allocated frequency and in the allocated time slots. When the mobile station has only control 15 information to transmit, on the other hand, the mobile station is not allocated any resource for the uplink data channel, and transmits the control information to the base station on an uplink control channel which is a radio resource previously set for transmission of control 20 information. The control information which is transmitted on the uplink includes ACK (ACKnowledgement)/NACK (Negative ACKnowledgement) which is a response to data from the base station, and CQI (Channel Quality Indicator) which is a measure of the quality of downlink 25 communication (for example, refer to non-Patent Literature 2). By the way, the base station preferentially 6072332-1 -3 allocates a frequency band with the best uplink communication quality for the uplink data channel, from the available frequency band between the base station and the mobile station. Therefore, before being allocated a 5 resource for the uplink data channel, the mobile station needs to transmit to the base station a wideband pilot signal (SRS: Sounding Reference Signal) that is used for measuring the quality of uplink communication. In this case, there arises a problem of how to multiplex control 10 information and SRS when a same or different mobile stations transmit them simultaneously. To tackle this problem, the following multiplexing scheme has been proposed (for example, refer to non-Patent Literature 3). FIG. 21 illustrates an example of uplink signals 15 including SRS. In this example of FIG. 21, ACK is transmitted as control information with two frequency bands as uplink control channels i and j. The mobile station is permitted to use one of these uplink control channels i and j to transmit the control information. On 20 each uplink control channel, a signal indicating control information and a pilot signal (RS (Reference Signal)) are scheduled in a predetermined order. However, in a predetermined portion of a unit time period, all frequency bands are reserved as a radio resource for SRS 25 transmission. When transmitting SRS, the mobile station uses the reserved resource in the predetermined portion of the unit time period. 6072332-1 A -4 Non-Patent Literature 1: 3rd Generation Partnership Project, "Evolved Universal Terrestrial Radio Access (E UTRA) and Evolved Universal Terrestrial Radio Access (E UTRAN) ; Overall description; Stage 2 (Release 8) ", 3GPP 5 TS36.300, 2007-06. V8.1.0. Non-Patent Literature 2: 3rd Generation Partnership Project,.. "Physical Channels and Modulation (Release 8)", 3GPP TS36.211, 2007-05, V1.1.0. Non-Patent Literature 3: 3rd Generation Partnership 10 Project, "Multiplexing of Sounding RS and PUCCH", 3GPP TSG-RAN WG1 #49bis R1-072756, 2007-6. However, the time multiplexing scheme employed in the non-Patent Literature 3 does not permit control information to be transmitted at the same time as a 15 wideband signal to be used for measuring communication quality.' Therefore, as compared with the case of not multiplexing a wideband signal and a control information signal, this scheme provides less radio resources available in every unit time period on every uplink 20 channel. This causes problems that the quality of receiving a signal indicating control information deteriorates at a receiving apparatus (corresponding to the above-described base station on the uplink) and that the number of transmitting apparatuses (corresponding to 25 the aboVe-described mobile station on the uplink) which can be covered by each control channel decreases. 6072332-1 -5 Summary of Invention Disclosed is a transmitting apparatus, receiving apparatus, and communication method, which can prevent deterioration in the quality of data transmission and 5 reception even when measurement of communication quality using & wideband signal and data transmission and reception using a predetermined frequency band are performed around the same time. In accordance with a first aspect of the invention, 1c there is provided a radio communication method in a radio communication system for performing communication between a transmitting apparatus and a receiving apparatus for both data transmission at a first frequency and the data transmission at a second frequency. The radio 15 communication method comprises transmitting from the transmitting apparatus a signal to be used by the receiving apparatus for measuring communication quality, in a first frequency band in a given portion of a first time period, the first frequency band having a wider 20 bandwidth than a frequency band used for the data transmission and not including the first frequency; transmitting from the transmitting apparatus the signal in a second frequency band in a given portion of a second time period coming after the first time period, the second 25 frequency band having a wider bandwidth than the frequency band used for thd data transmission and not including the second frequency; receiving by the receiving apparatus the 6072332-1 -6 signal which is transmitted from the transmitting apparatus in the first frequency band in the given portion of the first time period; and receiving by the receiving apparatus the signal which is transmitted from the 5 transmitting apparatus in the second frequency band in the given portion of the second time period. According to the aspects of the present invention, a signal to be used for measuring communication quality is transmitted in a first time period in a frequency band 10 which does not include a first frequency, and then is transmitted in a., second time period in a frequency band which does not include a second frequency. Therefore, there exists a frequency band without interference of the signal in each of the first and second time periods. This 15 can prevent quality deterioration in data transmission and reception. In addition, using the signal transmitted in the first time period and transmitted in the second time period enables measurement of quality of a wide range of frequencies. 20 The above and other objects, features and advantages of the present invention will become apparent from the following description when taken in conjunction with the accompanying drawings which illustrate preferred embodiments of the present invention by way of example. 25 Brief Description of the Drawings FIG. 1 illustrates an overview of an embodiment. 6072332-1 -7 FIG. 2 illustrates a system configuration of the embodiment. FIG. 3 is a block diagram illustrating functions of a mobile station according to a first embodiment. 5 FIG. 4 is a block diagram illustrating functions of a base station. FIG. 5 illustrates a frame structure. FIG. 6 illustrates allocation of downlink channels. FIG. 7 illustrates allocation of uplink channels. 10 FIG. 8 illustrates an example of uplink signals including ACK according to the first embodiment. FIG. 9 illustrates an example of uplink signals including CQI according to the first embodiment. FIG. 10 illustrates another example of uplink 15 signals including ACK according to the first embodiment. FIG. 11 illustrates another example of uplink signals including CQI according to the first embodiment. FIG. 12 is a sequence diagram illustrating allocation control in the case where SRS and uplink data 20 overlap. FIG. 13 is a sequence diagram illustrating allocation control in the case where SRS and ACK overlap. FIG. 14 illustrates an example of uplink signals including ACK according to a second embodiment. 25 FIG. 15 illustrates an example of uplink signals including CQI according to the second embodiment. FIG. 16 is a block diagram illustrating functions 6072332-1 -8 of a mobile station according to a third embodiment. FIG. 17 illustrates an example of uplink signals including ACK according to the third embodiment. FIG. 18 illustrates an example of uplink signals 5 including CQI according to the third embodiment. FIG. 19 illustrates another example of uplink signals including ACK according to the third embodiment. F1'G. 20 illustrates another example of uplink signals including CQI according to the third embodiment. 10 FIG. 21 illustrates an example of uplink signals including SRS. Best Mode for Carrying out the Invention Hereinafter, embodiments of the present invention 15 will be described in detail with reference to the accompanying drawings. The description begins with an overview of an embodiment to be discussed herein and then proceeds to the details of those embodiments. FIG. 1 illustrates an overview of an embodiment. 20 The communication system in FIG. 1 is for data transmission and reception at a plurality of frequencies, and includes a transmitting apparatus 1 and a receiving apparatus 2. The transmitting apparatus 1 is a communication 25 apparatus that transmits data by radio to the receiving apparatus 2. The transmitting apparatus 1, for example, is equivalent to a mobile station of a mobile telephone 6072332-1 -9 system. The transmitting apparatus 1 includes a transmitter la which transmits to the receiving apparatus 2 a signal to be used for measuring the quality of radio communication from the transmitting apparatus 1 to the 5 receiving apparatus 2. In more detail, the transmitter la transmits a wideband signal which occupies a wider frequency band than is used for data transmission, in a given portion of a first time period in a frequency band which does not 10 include a first frequency. Then, the transmitter la transmits the wideband signal in a given portion of a second time period coming after the first time period in a frequency band which does not include a second frequency. The receiving apparatus 2 is a communication 15 apparatus that receives data by radio from the transmitting apparatus 1. The receiving apparatus 2, for example, is equivalent to a base station of a mobile telephone system. The receiving apparatus 2 includes a quality measuring unit 2a. The quality measuring unit 2a 20 measures the quality of radio communication from the transmitting apparatus 1 to the receiving apparatus 2, based on the wideband signal received from the transmitting apparatus 1 in the first and second time periods., The measured quality of radio communication may 25 be used as an index for selecting a frequency band to be allocated to the transmitting apparatus 1, for example. In such the communication system, the transmitter .6072332-1 -10 la of the transmitting apparatus 1 uses a frequency band which does not include the first frequency in a given portion of the first time period and uses a frequency band which does not include the second frequency in a given 5 portion of the second time period in order to transmit a wideband signal. Then, the quality measuring unit 2a of the receiving apparatus 2 measures the quality of radio communication from the transmitting apparatus 1 to the receiving apparatus 2 based on the wideband signal 10 received in the first and second time periods. In general, the measurement of communication quality needs a signal over a wide range of frequencies. However, if a transmitted signal occupies all of the frequency bands available for communication between the 15 transmitting apparatus 1 and the receiving apparatus 2, data transmissiotY and reception is inhibited during this transmission. The above technique enables the use of at least. the first frequency without interference of the wideband signal during the first time period and the use 20 of at least the second frequency without interference of the wideband signal during the second time period. Therefore, this technique makes it possible to prevent deterioration in communication quality due to a reduction in time period available for data transmission 25 and reception. Farther, the receiving apparatus 2 can use the wideband signal received in the first and second time periods,-which makes it possible to measure the quality of 6072332-1 -11 a wide range of frequencies. (First Embodiment) Hereinafter, the first embodiment will be described in detail with reference to the accompanying drawings. 5 FIG. 2 illustrates a system configuration according to the embodiment. A mobile communication system according to th6 embodiment is a radio communication system where packet data is transmitted. The mobile communication system in FIG. 2 includes mobile stations 10 100 and 100a and a base station 200. The mobile stations 100 and 100a are mobile telephones, for example. While in the communication range (cell) of the base station, the mobile stations 100 and 100a are capable of performing radio communication with 15 the base station, and transmitting and receiving packet data with an unillustrated computer or another mobile station via the base station. The packet data which the mobile stations 100 and 100a transmit and receive includes VoIP (Voice over Internet Protocol) data, electronic mail 20 data, and image dgta. The base station 200 constantly monitors mobile stations existing in its cell, and performs wire or radio communication with other base stations where appropriate. Upon receipt of a radio communication request from a 25 mobile station- existing in the cell or a radio communication request for communication with a mobile station existing in the cell, the base station 200 6072332-1 - -12 transmits and receives various control information and packet data with the mobile station. FIG. 3 is a block diagram illustrating functions of a mobile station according to the first embodiment. The 5 mobile station 100 includes a transmitting and receiving antenna 110, a data processor 120, a pilot signal processor 130, a control information processor 140, a resource selector 150, a transmitter 160, a receiver 170, and a downlink quality measuring unit 180. 10 The transmitting and receiving antenna 110 is an antenna to be used for transmission and reception, and is designed to transmit by radio uplink signals output from the transmitter 160 to the base station 200, and to receive downlink signals transmitted by radio from the 15 base station 200 and pass the signals to the receiver 170. The data processor 120 generates packet data to be transmitted by radio, and encodes and outputs the data. For example, thendata processor 120 generates VoIP data, electronic mail data, image data, etc. in response to 20 operational inputs from the user of the mobile station 100. The pilot signal processor 130 generates various types of pilot signals. An encoding pattern is defined for each type of pilot signals. Pilot signals that the pilot signal processor 130 generates include SRS to be 25 used for measurement of uplink communication quality. The control information processor 140 generates control information to be transmitted by radio, and 6072332-1, -13 encodes and outputs the information according to prescribed rules. The control information that the control information processor 140 generates includes ACK/NACK which is a response to packet data from a base 5 station, CQI which is a measure of downlink communication quality, an uplink radio resource allocation request, etc. More specifically, when supplied with a measure of downlink communication quality from the downlink quality measuring unit 18!0, the control information processor 140 10 generates CQI. The resource selector 150 manages uplink radio resources available to the mobile station 100. The resource selector 150 occasionally receives, from the receiver 170, control information (UL allocation grant 15 information) indicating an uplink radio resource allocated by the base station 200. In addition, the resource selector 150 provides the transmitter 160 with information about the allocation of radio resources. The transmitter 160 identifies radio resources to 20 be used for transmission of packet data, pilot signal, and control information based on the allocation information provided by thg resource selector 150. Then the transmitter 160 modulates and multiplexes the packet data signal, pilot signal, and control information signal, and 25 outputs the resultant to the transmitting and receiving antenna 110. This embodiment employs SC-FDMA or OFDMA as a multiplexing scheme. 6072332-1*4 -14 Upon receipt of received signals via the transmitting and receiving antenna 110, the receiver 170 checks the signals to determine whether they contains a signal addressed to the own station. If such a signal is 5 detected, the receiver 170 demodulates and decodes the signal. Packet data included in the received signal, if there is, is taken inside. The mobile station 100 processes the packet data according to its type. For example, in the case of VoIP data, the mobile station 100 10 outputs sounds from a speaker. In the case of electronic mail or image data, the mobile station 100 displays text or images on a display screen. UL allocation grant information included in the received, signal, if there is, the receiver 170 passes the 15 information to the resource selector 150. The receiver 170 also extracts a signal to be used for measuring downlink communication quality from the received signal, and passes the signal to the downlink quality measuring unit 180. 20 The downlink quality measuring unit 180 measures the communicatidYi quality of a plurality of downlink frequency bands based on the signal supplied from the receiver- 170. Then the downlink quality measuring unit 180 supplies the measurement result to the control 25 information processor 140. Note that the mobile station 100a may be designed to have the same. module configuration as the mobile 6072332-1 -15 station 100. FIG. 4 is a block diagram illustrating functions of a base station. , The base station 200 includes a transmitting and receiving antenna 210, a data processor 5 220, a pilot signal processor 230, a control information processor 240, a resource manager 250, a scheduler 260, a transmitter 270, a receiver 280, and an uplink quality measuring unit 290. The transmitting and receiving antenna 210 is an 10 antenna for transmission and reception. The transmitting and receiving antenna 210 transmits, by radio, downlink signals output from the transmitter 270. The transmitting and receiving antenna 210 also receives uplink signals transmitted by radio from the mobile stations 100 and 100a, 15 and passes them to the receiver 280. If there is packet data to be transmitted by radio to a mobile station 100, 100a existing in the cell, the data processor 220 encodes and outputs the data. For example, when supplied with VoIP data, electronic mail 20 data, image data, or another data which is addressed to a mobile station 100; 100a, the data processor 220 encodes and outputs the data. The pilot signal processor 230 generates various types of pilot signals which enable the mobile station 100, 25 100a to reproduce correctly packet data from radio signals. An encoding pattern is defined for each type of pilot signals. 6072332-1 -16 The control information processor 240 generates control .information to be transmitted by radio, and encodes and outputs the information according to predetermined rules. The control information which the 5 control information processor 240 generates includes information for demodulation and decoding, such as the encoding scheme of packet data and a radio resource used for transmission of the packet data, and UL allocation grant informatiorP indicating allocation of an uplink radio 10 resource. The resource manager 250 manages downlink and uplink radio resources between the base station 200 and the mobile statig9ns 100 and 100a existing in the cell. The resource manager 250 provides the scheduler 260 and 15 the receiver 280 with information about the current state of allocation of radio resources. In allocating an uplink radio resource to a mobile station 100, 100a, the resource manager 250 refers to the measurement results of communication quality supplied from the uplink quality 20 measuring unit 290. The resource manager 250 preferentially allocates a frequency band with good communication qu4ity. The scheduler 260 determines radio resources to be used for transmission of packet data, pilot signal, and 25 control information which are addressed to each mobile station, based on the information about the current state of allocation of downlink radio resources supplied from 6072332-1 -17 the resource manager 250. This embodiment employs OFDMA as a multiplexing scheme. In accordance with instructions from the scheduler 260, the transmitter 270 modulates and multiplexes the 5 packet data signal, pilot signal, and control information signal, and outputs the resultant to the transmitting and receiving antenna 210. When supplied with received signals from the transmitting and receiving antenna 210, the receiver 280 10 demodulates and decodes a signal transmitted from each of the mobile stations 100 and 100a existing in the cell, with reference to the information of the uplink radio resource allocation supplied from the resource manager 250. Packet data included in the received signal, if there is, 15 is taken. inside. The base station 200 transfers the taken packet data to its destination computer or mobile station. If the received signal includes control information requesting allocation of a radio resource, then the receiver 280 passes the information to the resource 20 manager 250. If the received signal includes SRS, then the receiver 280 passes the SRS to the uplink quality measuring unit 29'0. When supplied with the SRS from the receiver 280, the upl-ink quality measuring unit 290 measures the 25 communication quality of a plurality of uplink frequency bands based on the SRS. The uplink quality measuring unit 290 then supplies the measurement result to the resource 6072332-1 -18 manager 250. FIG. 5 illustrates a frame structure. FIG. 5 schematically depicts the structure of a frame which is transmitted and received between the mobile stations 100 5 and 100a; and the base station 200. Each frame has a time length of 10 ms, and has a plurality of subframes with a time length of 1 gs. Each subframe is further divided in both the frequency domain and the time domain for radio resource 10 allocation management. A minimum unit for allocation in a frequency axis is called a subcarrier, and a minimum unit for allocation in a time axis is called a symbol. A smallest unit of radio resource allocation, represented by one subcarrier and one symbol, is called a resource 15 element. In this connection, the first and second halves of the 1-ms subframe, each of which therefore has 0.5 ms, are called slots, respectively. That is to say, one subframe has two slots. Such radio resources are used for uplink and 20 downlink control channels and uplink and downlink data channels. When a signal is transmitted, a guard interval called CP (Cyclic Prefix) is inserted at the beginning of each symbol so as to prevent interference between signals due to propagation delay. Here, two types of CPs (Short 25 CP and Long CP) having different time lengths are employed. FIG. 6 illustrates allocation of downlink channels. FIG. 6 schematically depicts the structure of a subframe 6072332-1 -19 which is transmitted on the downlink from the base station 200 to the mobile stations 100 and 100a. For the downlink, radio resources are allocated to downlink control channels and downlink data channels to the mobile stations. 5 Each downlink control channel is allocated a radio resource having ' predetermined symbol length from the beginning of a subframe. In general, one to three symbols from the beginning of the subframe are allocated. The frequencies of the downlink control channels to a 10 plurality of mobile stations are multiplexed. The mobile station 100, 100a detects a downlink control channel for the own station out of the plurality of downlink control channels whose frequencies are multiplexed. The downlink control channel is used for transmitting information 15 indicating an encoding scheme of data included in a downlink data channel and a radio resource used for the downlink* data channel, and UL allocation grant information. Each downlink data channel is allocated a radio resource other than radio resources used for the downlink 20 control channels. The frequencies of downlink data channels to a plurality of mobile stations are multiplexed. The downlink data channels and downlink control channels are time-multiplexed. The mobile station 100, 100a refers to the control information transmitted on the downlink 25 control channel to identify the radio resource of the downlink 4 data channel for the own station. An amount of radio resource to be used for a downlink data channel is 6072332-1 -20 variable. The downlink data channel is used for transmission of packet data. The above downlink control channel may be represented as PDCCH (Physical Downlink Control Channel) 5 while the above downlink data channel may be represented as PDSCH (Physical Downlink Shared Channel). FiG. 7 illustrates allocation of uplink channels. FIG. 7 schematically depicts the structure of a subframe which is transmitted on the uplink from the mobile 10 stations 100 and 100a to the base station 200. For the uplink, radio resources are allocated to uplink control channels each of which is shared by a plurality of mobile stations and uplink data channels each of which is used by one mobile station. 15 Each uplink control channel is allocated a radio resource of a predetermined frequency band including one of two limiting frequencies, or the frequency bands located at both GIedges of the transmission band, of the entire frequency band available between the mobile 20 stations.
4 100 and 100a and the base station 200. Here, two uplink control channels are provided for the uplink. One uplink control channel uses a high frequency radio resource in the first half slot and a low frequency radio resource in the second half slot 25 (represented as uplink control channel i in FIG.7). The other uplink control channel uses a low-frequency radio resource in the first half slot and a high-frequency radio 6072332-1, -21 resource*- in the second half slot (represented as uplink control channel j in FIG. 7). One of the .two uplink control channels is allocated to each mobile station 100, 100a by the base station 200. 5 The base station 200 indirectly manages this allocation to the mobile stations 100 and 100a through the allocation of downlink control channels for the downlink. More specifically, uplink control channels are allocated according to the allocation of downlink control channels 10 in such a way that a mobile station allocated the downlink control channel i in FIG. 6 uses the uplink control channel i, a mobile station allocated the downlink control channel j uses the uplink control channel j, and a mobile station allocated the downlink control channel k uses the 15 uplink control channel i. The uplink control channel is used for transmitting ACK/NACK, CQI, and requests for allocation of radio resources, etc. On each uplink control channel, control information from a plurality of mobile stations is encoded, 20 multiplexed, and then transmitted. Normally, one uplink control channel allows transmission of control information from six mobile stations. If the base station 200 has many mob.le stations, the base station 200 secures a wider frequency band for the uplink control channels, thereby 25 enabling many mobile stations to transmit control information on the uplink control channels. Each uplink data channel is allocated a frequency 6072332-1 -22 band other than frequency bands used for the uplink control channels. The frequencies of uplink data channels from a plurality of mobile stations are multiplexed. A mobile station 100, 100a identifies a usable radio 5 resource for an uplink data channel based on UL allocation grant information" received on a downlink control channel. The uplink data channel is used for transmission of packet data.- In addition, the uplink data channel may be used for transmission of control information as well. 10 The mobile station 100, 100a determines which one of an uplink control channel and an uplink data channel is appropriate to use.for transmission of control information, based on whether or not having being assigned an uplink data channel by the base station 200. More specifically, 15 if an uplink data channel has been assigned, the mobile station 100, 100a uses the uplink data channel to transmit the control information together with packet data. If no uplink data channel has been assigned, on the contrary, the mobile stat on 100, 100a uses an uplink control 20 channel to transmit the control information. By the way, on the uplink, SRS, which is a wideband signal, may be transmitted, other than signals on the uplink control channels and uplink data channels. SRS is transmitted from the mobile station 100, 100a in response 25 to an instruction from the base station 200. The following describes how to multiplex SRS and other signals on the uplink. 6072332-1 -23 FIG. 8 illustrates an example of uplink signals including ACK according to the first embodiment. FIG. 8 describes how to allocate radio resources in the case where a signal indicting ACK and SRS are multiplexed in a 5 subframe with Short CP. The subframe with Short CP includes 14 symbols. The first half seven symbols constitute a slot, and so do the second half seven symbols. Ig each of the first and second half slots of an uplink control channel i, four out of the seven symbols 10 are allocated for ACK while the other three are allocated for RS (pilot signal) . More specifically, the symbols are allocated for ACK, ACK, RS, RS, RS, ACK, and ACK, in order from the first symbol. Note that one bit is sufficient for an ACK/NACK signal, and so the same signal is 15 transmitted in the symbols allocated for ACK. Similarly to the uplink control channel i, in each of the tirst and second half slots of an uplink control channel j, four out of the seven symbols are allocated for ACK while the other three are allocated for RS. However, 20 when one or more mobile stations transmit SRS, the first symbol of each slot is used for the SRS transmission and -is not used for the ACK transmission. A wideband radio resource which is allocated for SRS does not include the frequency band of the uplink 25 control channel i but does include the frequency band of the uplink control channel j. In this connection, it is preferable that the frequency band of the uplink control 6072332-1 -24 channel i and that for the SRS transmission are not consecutive. This is because an increase in the number of mobile stations belonging to the base station 200 may increase the necessity of providing a wider frequency band 5 for the uplink control channel i. In the radio resource allocated for SRS, SRSs from a plurality of mobile stations can be encoded, multiplexed, and then transmitted. That is, the mobile stations 100 and 100a can transmit their SRSs simultaneously. Note 10 that the mobile station 100, 100a does not output a signal over .all, frequencies of the radio resource allocated for SRS, but selects parts of the frequencies and outputs the signal. This is because based on the communication quality of selected frequency parts, the communication 15 quality of other frequencies can be estimated. Consider the case where the mobile stations 100 and 100a exist in the same cell, and one mobile station 100 transmits SRS and the other mobile station 100a does not. In this case, the base station 200 allocates the mobile 20 station -. 100, which is supposed to transmit SRS, a radio resource to be used for SRS transmission and the uplink control channel j as an uplink control channel. According to this allocation, the mobile station 100 transmits the SRS in the first symbol of each slot. 25 In order to transmit ACK besides SRS in the same subframe, the mobile station 100 uses the uplink control channel j in symbols other than the first symbol of each 6072332-1j.
-25 slot.. However., if the mobile station 100 has an uplink data channel assigned by the base station 200, the mobile station 100 transmits the ACK on the uplink data channel, not on the uplink control channel j. In this case, the 5 mobile station 100, avoids using the first symbol in each slot as well. - On the other hand, the base station 200 allocates the uplink control channel i as an uplink control channel to the mobile station 100a, which is not supposed to 10 transmit- SRS. The mobile station 100a uses the uplink control channel i to transmit ACK. At this time, the mobile station 100a can use all of the slots in the subframe. However, if the mobile station 100a has an uplink data channel assigned by the base station 200, the 15 mobile station 100a transmits the ACK on the uplink data channel, not on the uplink control channel i. In this case, the mobile station 100 avoids using the first symbol in each slot. The base station 200 gives the mobile station 100a an advance notice that the mobile station 100 20 is supposed to transmit SRS. If no mobie station transmits SRS in the cell, the base station 200 allocates the uplink control channel i to a mobile station moving at a slow speed and the uplink control channel j to a mobile station moving at a high 25 speed. This is because such a mobile station moving at a slow speed may transmit SRS at longer intervals as the quality of communication with the mobile station may not 6072332-1 -26 be measured frequently. FIG. 9. ilustrates an example of uplink signals including CQI according to the first embodiment. FIG. 9 describes how to allocate radio resources in the case 5 where a signal indicating CQI and SRS are multiplexed in a subframe with Short CP. In each of the first and second half slots of an uplink control channel i, five out of the seven symbols are allocated for CQI while the other two are allocated 10 for RS. More specifically, the symbols are allocated for CQI, CQI, RS, CQI, RS, CQI, and CQI, in order from the first symbol. Note that the CQI signal is divided and transmitted in a plurality of symbols. Similarly to the uplink control channel i, in each 15 of the first and second half slots of an uplink control channel j, five out of the seven symbols are allocated for CQI while the other two are allocated for RS. However, when one or more mobile stations transmit SRS, the first symbol is used for the SRS transmission, and is not used 20 for the CQI transmission. As described above for the case of ACK in FIG. 8, the uplink control channel j is allocated to a mobile station which is supposed to transmit SRS, and the uplink control channel i is allocated to a mobile station which 25 is not supposed to transmit SRS. Therefore, even when another mobile station transmits SRS, the mobile station which does not transmit SRS can use all symbols in the 6072332-1 -27 subframe for the CQI transmission on the uplink control channel. FIG. 10 illustrates another example of uplink signals including ACK according to the first embodiment. 5 FIG. 10 describes how to allocate radio resources in the case where a signal indicating ACK and SRS are multiplexed in a subframe with Long CP. A subframe with Long CP includes twelve symbols. The first half six symbols constitute a slots and so do the second half six symbols. 10 In each of the first and second half slots of an uplink control channel i, four out of the six symbols are allocated for ACK while the other two are allocated for RS. More specifically, the symbols are allocated for ACK, ACK, RS, RS, ACK, and ACK, in order from the first symbol. In 15 all of the symbols allocated for ACK, the same signal is transmitted. Similarly to the uplink control channel i, in each of the first andi second half slots of an uplink control channel j, four out of the six symbols are allocated for 20 ACK while the other two are allocated for RS. However, when one or more mobile stations transmit SRS, the first symbol is used for the SRS transmission, and is not used for the ACK transmission. As described above for the case of Short CP in FIG. 25 .8, the uplink control channel j is allocated to a mobile station which is supposed to transmit SRS, and the uplink control channel it is allocated to a mobile station which 6072332-1.
-28 is not supposed to transmit SRS. Therefore, even when another mobile station transmits SRS, the mobile station which does not transmit SRS can use all symbols in the subframe for the! ACK transmission on the uplink control 5 channel. FJG. 11 illustrates another example of uplink signals including CQI according to the first embodiment. FIG. 11 describes how to allocate resources in the case where a signal indicating CQI and SRS are multiplexed in a 10 subframe with Long CP. In each of the first and second half slots of an uplink control channel i, five out of the six symbols are allocated for CQ:while the other one is allocated for RS. More specifically, the symbols are allocated for CQI, CQI, 15 RS, CQI,4 CQI, and CQI, in order from the first symbol. Note that a CQI signal is divided and transmitted in a plurality of symbols. Similarly to the uplink control channel i, in each of the first and second half slots of an uplink control 20 -channel j, five out of the six symbols are allocated for CQI while the other one is allocated for RS. However, when one or more9'mobile stations transmit SRS, the first symbol is used for the SRS transmission, and is not used for the CQI transmission. 25 As described above for the case of Short CP in FIG. 9, the uplink control channel j is allocated to a mobile station which is supposed to transmit SRS, and the uplink 6072332-1 -29 control channell i is allocated to a mobile station which is not supposed to transmit SRS. Therefore, even when another mobile station transmits SRS, the mobile station which does not transmit SRS can use all symbols in the 5 subframe for the CQI transmission on the uplink control channel. FIGS. 8 to 11 describe how ACK or CQI, as an example of an uplink signal, is transmitted. Other types of control information can be transmitted in the same way. 10 In addition, not only one type of control information but also some types of control information can be transmitted in a same subframe. For example, ACK and CQI can be transmitted in a same subframe. The following describes how to control the radio 15 resource allocation between the mobile stations 100 and 100a and the base station 200. The following examples are the cases of multiplexing SRS and a signal on an uplink data channel and of multiplexing SRS and a signal on an uplink control channel. 20 . FIG. 12 is a sequence diagram illustrating allocation contrdil in the case where SRS and uplink data overlap. The sequence in FIG. 12 will be described step by step..., This explanation focuses on an uplink from the mobile station 100 to the base station 200. 25 (Step Sll). The base station 200 detects the necessity of measuring the communication quality of an uplink from the mobile station 100 to the base station 200. 6072332-1 -30 Then, the base station 200 allocates the mobile station 100 a radio resource to be used for SRS transmission and sets transmission intervals. Then, the base station 200 transmits the allocation information on a downlink control 5 channel. (Step S12),, The mobile station 100 transmits SRS with the radio resource allocated at step S11. The base station 200 measures the communication quality of the uplink based on the SRS received from the mobile station 10 100. (Step S13) After that, the mobile station 100 transmits SRS at the transmission intervals set at step S11, ~and accordingly the base station 200 measures the communication quality based on the received SRS. 15 (Step S14),. The mobile station 100 detects a request for transmitting packet data to the base station 200. The mobile station 100 then sends a request for radio resource allocation on the uplink control channel. (Step S15) The base station 200 allocates an 20 uplink data channel to the mobile station 100 in response to the allocation request received at step S14. At this time,~ the base station 200 selects a frequency band to be used,. based on the measurement results obtained at steps S12 and 13. . Then, the base station 200 transmits UL 25 allocation grant information on the downlink control channel . (Step S16) The mobile station 100 transmits the 6072332-1 -31 packet data on the uplink data channel allocated at step S15. (Step S17) The base station 200 newly allocates an uplink data channel to the mobile station 100 after 5 receiving the padket data from the mobile station 100, and then transmits UL allocation grant information on the downlinks control channel. After that, the transmission of the packet data from the mobile station 100 and the allocation of an, uplink data channel by the base station 10 200 are repeated until the transmission of the packet data is completed. (Step S18) The base station 200 detects overlapping transmission of SRS and packet data from the mobile station 100 when allocating an uplink data channel, 15 that is, detects that the SRS and packet data are to be transmitted in a same subframe. Then, the base station 200 sends a report of the overlap with the SRS transmission,. 1pgether with UL allocation grant information, on the downlink control channel. 20 (Step S19) The mobile station 100 transmits the SRS with the radio resource allocated at step S11. The base station 200 measures the communication quality of the uplink based on the SRS received from the mobile station 100. 25 (step S20) The mobile station 100 transmits the packet data on the uplink data channel allocated at step S18, in symbols! other than those used for the SRS 6072332-1 -32 .transmission. As described above, the mobile station 100 periodically transmits SRS in response to an instruction from the base station 200, and accordingly the base 5 station 0200 measures the communication quality of the uplink based on the received SRS. Then, upon receipt of a request for allocation of an uplink data channel, the base station 200 selects a frequency band to be allocated, based on the measurement results of the communication 10 quality. When SRS and a signal on an uplink data channel need to be multi'Plexed, the mobile station 100 transmits the packet data so that the uplink data channel for the packet data transmission does not overlap with the radio 15 resource for the SRS transmission. FIG. 13 .,is a sequence diagram illustrating allocation control in the case where SRS and ACK overlap. The sequence in FI.G. 13 will be described step by step. The following explanation focuses on an uplink from the 20 mobile station 100 to the base station 200. (Step S217 The base station 200 detects the necessity of measuring the communication quality of an uplink from the mobile station 100 to the base station 200. Then the base station 200 allocates the mobile station 100 25 a radio resource,, to be used for SRS transmission, sets transmission intervals, and then transmits the allocation information on a downlink control channel. 6072332-1 -33 (Step S22) The mobile station 100 transmits SRS with the radio resource allocated at step S21, and the base station 200 measures the communication quality of the uplink based on the SRS received from the mobile station 5 .100. (Step S23) After that, the mobile station 100 transmits SRS at transmission intervals set at step S21, and accordingly the base station 200 measures the communication quality based on the received SRS. 10 (Step S24) The base station 200 obtains packet data addressed. to the mobile station 100. Then the base station 200 sends a report of the radio resource used for a downlink data channel, on the downlink control channel, and also transmits the packet data on the downlink data 15 channel. (Step S25)"' In response to the packet data received at step S24, the mobile station 100 transmits ACK or NACK on the uplink control channel. More specifically, the mobile station 100 transmits ACK if demodulation and 20 decoding of the ,packet data is successfully completed. The mobile station 100 transmits NACK, on the contrary, if the demodulation and decoding is not successful. (Step S26) The base station 200 sends a report of the radio resource used for a downlink data channel, on 25 the downlink control channel, and also transmits packet data on the downlink data channel. The packet data to be transmitted here is packet data to be transmitted after 6072332-1 -34 the ACK is received at step S25. If the NACK is received, then the packet data transmitted last time is transmitted again. After that, the transmission of ACK/NACK response from the mobile station 100 and the transmission of the 5 packet data from the base station 200 are repeated until the transmission sof the packet data is completed. (Step S27) When allocating a downlink data channel, the base station 200 detects overlapping transmission of SRS and ACK/NACK from the mobile station 100, that is, 10 detects that the SRS and ACK/NACK are to be transmitted in a same subframe. Then, the base station 200 allocates different uplink control channels to the mobile station .100 and other mobile stations which are not supposed to transmit SRS. The allocation of uplink data channels is 15 changed by changing the allocation of downlink control channels. Then the base station 200 sends a report of the radio. resource used for a downlink data channel, on a downlink control channel, and also transmits the packet data on the downlink data channel. 20 (Step S28) The mobile station 100 transmits SRS with the radio resource allocated at step S21, and the base station 200 measures the communication quality of the uplink based on the SRS received from the mobile station 100. 25 (Step S29) As a response to the packet data at step S27-., the mobile station 100 transmits ACK or NACK on the uplink control channel, in symbols other than those 6072332-1 -35 used for the SRS transmission. As described above, in response to an instruction from the base station 200, the mobile station 100 periodically transmits SRS, and accordingly the base 5 station 200 measures the communication quality of the uplink based on the received SRS. When obtaining packet data addressed to the mobile station 100, the base station 200 transmits the packet data on a downlink data channel. Upon receipt of tthe packet data, the mobile station 100 10 transmits an ACK/NACK response. If SRS and an ACK/NACK signal need to be multiplexed, then the base station 200 allocates different uplink control channels to the mobile station 100 and other mobile stations which are not supposed to transmit 15 SRS. The mobile station 100 transmits the ACK/NACK so .that the uplink control channel for the ACK/NACK transmission does not overlap with the radio source for the SRS transmission. The above explanation describes the case where the 20 same .mobile station transmits packet data or control information, and SRS. The same control can be applied to the case where different mobile stations transmit them. In the above-described communication system, one of two uplink control channels can be used without 25 interference of SRS, even in a subframe including the SRS transmission. Therefore, SRS and a control information signal can be multiplexed so as not to cause deterioration 6072332-1, -36 in communication quality. In addition, by using both SRS which- is received in the first half slot and the SRS which is received in the second half slot, the base station can measure the quali, y of a wide range of frequencies. 5 (Second Embodiment) The second embodiment will now be described in detail with reference to the accompanying drawings. This section focuses on differences from the aforementioned first embodiment, and will omit explanation of same 10 features. A communication system according to the second embodiment uses one subframe, not one slot, as an interval of transmission of a pair of two SRSs. The communication system according to the second embodiment can be realized by the same configuration as 15 that according to the first embodiment. A mobile station and base station according to the second embodiment can be realized by the same module configurations as the mobile station 100 and base station 200 of FIGS. 3 and 4 according to the first embodiment, respectively. However, 20 the second embodiment transmits and receives SRS and measures the communication quality at different times from the first embodigIent. The following description of the second embodiment uses the same reference numbers of the mobile station and base station as the first embodiment. 25 FIG. 14 illustrates an example of uplink signals including ACK according to the second embodiment. FIG. 14 illustrates how to allocate radio resources in the case 6072332-1' -37 where a signal indicating ACK and SRS are multiplexed in two consecutive spbframes with Short CP. In each slot of an uplink control channel i, four out of the seven symbols are allocated for ACK while the 5 other three symbols are allocated for RS. More specifically, the symbols are allocated for ACK, ACK, RS, RS, RS, ACK, and ACK, in order from the first symbol. However, when one or more mobile stations transmit SRS, the first symbol of the second subframe is used for the 10 SRS transmission, and is not used for the ACK transmission. Similarly tto the uplink control channel i, in each slot of an uplink control channel j, four out of the seven symbols are allocated for ACK while the other three are allocated for RS. However, when one or more mobile 15 stations transmit SRS, the first symbol of the first subframe is used for the SRS transmission, and is not used for the ACK transmission. In the first symbol of the first subframe, a wideband radio resource which is allocated for SRS does 20 not include theN frequency band of the uplink control channel i but does include that of the uplink control channel *j. In. the first symbol of the second subframe, a wideband radio resource which is allocated for SRS includes the frequency band of the uplink control channel 25 i but does not include that of the uplink control channel A mobile station which is supposed to transmit SRS 6072332-1 -38 is allocated the uplink control channel j of the first subframe and the.uplink control channel i of the second subframe. On the other hand, a mobile station which is not supposed to transmit SRS is allocated the uplink 5 control channel i of the first subframe and the uplink control channel j of the second subframe. Therefore, the mobile station which does not transmit SRS but does transmit ACK on an uplink control channel can use all symbols in the subframes even when another mobile station 10 transmits SRS. In addition, the base station 200 can measure communication quality based on the SRSs received in the first symbols of two consecutive subframes. FIG. 15 illustrates an example of uplink signals including CQI according to the second embodiment. FIG. 15 15 illustrates an example of how to allocate radio resources in the case where a signal indicating CQI and SRS are multiplexed in two consecutive subframes with Short CP. Ii each slot of an uplink control channel i, five out of the seven symbols are allocated for CQI while the 20 other two are allocated for RS. More specifically, the symbols are allocated for CQI, CQI, RS, CQI, RS, CQI, and CQI, in prder from the first symbol. However, when one or more mobile stations transmit SRS, the first symbol of the second subframe is used for the SRS transmission, and is 25 not used for the CQI transmission. Similarly to, the uplink control channel i, in each slot of an uplink control channel j, five out of the seven 6072332-1 -39 symbols are allocated for CQI while the other two are allocated for RS.' However, when one or more mobile stations transmit SRS, the first symbol of the first subframe is used for the SRS transmission, and is not used 5 for the CQI transmission. As described for the example of ACK in FIG. 14, a mobile station which is supposed to transmit SRS is allocated the uplink control channel j of the first subframe and thel:iuplink control channel i of the second 10 subframe. On the other hand, a mobile station which is not supposed to transmit SRS is allocated the uplink control channel i of the first subframe and the uplink control channel j of the second subframe. Therefore, a mobile station which does not transmit SRS but does 15 transmit CQI on an uplink control channel can use all symbols in the subframes even when another mobile station transmits SRS. Then, the base station 200 can measure the communication quallity based on the SRSs received in the first symbols of two consecutive subframes. 20 FIGS. 14 and 15 illustrates how ACK or CQI, as an example of an uplink signal, is transmitted. The same technique can be applied for transmitting other types of control information. In addition, not only one type of control information but also different types of control 25 information can be transmitted in a same subframe. For example, ACK and CQI can be transmitted in a same subframe. In addition, FIGS. 14 and 15 illustrate an example of 6072332-1.4 -40 Short. CP. However, Long CP can be used as described in the first embodiment. Such the communication system can provide the same effects as that of the first embodiment. In addition, the 5 communication system according to the second embodiment can suppress a decrease in the number of signals to be time-multiplexed with SRS on an uplink control channel. (Third Embodiment) The third embodiment will now be described in 10 detail with reference to the accompanying drawings. This section focuses on differences from the aforementioned first embodiment, and will omit explanation of same features. A communication system according to the third embodiment allows a mobile station to perform antenna 15 diversity transmission, that is, to perform radio communication with a plurality of antennas. The communication system according to the third embodiment can be realized by the same system configuration as that according to the first embodiment of 20 FIG. 2, except that a mobile station and base station of the third embodiment perform antenna diversity. The mobile station and base station of the third embodiment are given reference numbers 100b and 200a, respectively. FIG. 16 is a block diagram illustrating functions 25 of a mobile station according to the third embodiment. The mobile station 100b includes transmitting and receiving antennas 110 and 110b, a data processor 120, a 6072332-1 -41 pilot signal processor 130, a control information processor 140, a resource selector 150b, a transmitter 160b, a receiver'! 170b, and a downlink quality measuring unit 180. The data processor 120, pilot signal processor 5 130, -control information processor 140, and downlink quality measuring unit 180 have the same functions of the corresponding components in the first embodiment of FIG. 3. The transmitting and receiving antennas 110 and 110b are antennas for transmission and reception. Each 10 transmitting and receiving antenna 110, 110b transmits uplink signals output from the transmitter 160b by radio to the base station 200a. In addition, the transmitting and receiving antenna 110, 110b receives downlink signals transmitted by radio from the base station 200a, and 15 passes the signals to the receiver 170b. At the time of transmission, the transmitter 160b selects one of the transmitting and receiving antennas 110 and 110b. The resource selector 150b manages uplink radio -resources which are available to the mobile station 100b. 20 In addition, the resource selector 150b manages switching between the transmitting and receiving antennas 110 and 110b for use in radio transmission. The resource selector 150b provides the transmitter 160b with information on the current state of allocation of radio resources and a 25 choice of which antenna to use. The transmitter 160b identifies radio resources to be used for transmission of pilot data, pilot signal, and 6072332-1 -42 control information, based on the information provided by the resource selector 150b. The transmitter 160b also selects a transmitting and receiving antenna to be used .for each transmission, based on the information provided 5 by the resource selector 150b. Then the transmitter 160b modulates and fiultiplexes signals, and outputs the resultant to the selected transmitting and receiving antenna.,. When receiving signals via the transmitting and 10 receiving antennas 110 and 110b, the receiver 170b selects either signal with a high reception quality, and then demodulates and decodes a signal addressed to the own station out of the selected received signal. Packet data included in the received signal, if there is, is taken 15 inside. The receiver 170b passes the resource selector 150b UL allocation grant information included in the received signal, if there is. If control information to instruct antenna switching is included in the received signal, then 20 the receiver 170b passes the information to the resource selector 150b. In addition, the receiver 170b supplies -the downlink quality measuring unit 180 with a signal to be used for measuring the communication quality of the downlink out of the received signal. 25 A control method for the antenna switching of the resource- selector 150b includes open-loop control and closed-loop control. In the open-loop control, the 6072332-1 -43 resource selector 150b switches between the transmitting and receiving antennas 110 and 110b as scheduled. For example, the resource selector 150b periodically switches between the transmitting and receiving antennas 110 and 5 110b. In the closed-loop control, on the other hand, the resource selector 150b switches between the transmitting and receiving antennas 110 and 110b in response to an instruction fromthe base station 200a. The base station 10 200a instructs which antenna to use, based on, for example, the communication qualities of signals received from the respective transmitting and receiving antennas 110 and 110b. The control method to be adopted is previously set 15 in the resource selector 150b. This embodiment employs the closed-loop control. The base station 200a according to the third embodiment can * be realized by the same module configuration as the base station 200 of the first 20 embodiment of FIG. 4, except that communication quality is measured by each of the transmitting and receiving antennas 110 and jl0b provided in the mobile station 100b. FIG. 17 illustrates an example of uplink signals including ACK according to the third embodiment. FIG. 17 25 illustrates how to allocate radio resources in the case where a signal indicating ACK and SRS are multiplexed in a subframe with Short CP. Upper signals are signals that 6072332-14 -44 are transmitted from the transmitting and receiving antenna 110 to the base station 200a while lower signals are signals that are transmitted from the transmitting and receiving antenna 110b to the base station 200a. Note 5 that FIG. 17 does not illustrate any signals which are transmitted from other mobile stations. As in the aforementioned first embodiment, the mobile station 100b which is supposed to transmit SRS is allocated an uplink control channel j. It is now assumed 10 that the.,mobile station 100b selects the transmitting and receiving antenna 110 for radio transmission. Then, the mobile station 110b transmits ACK and RS signals on the uplink control channel j from the transmitting and receiving antenna , 110. The mobile station 110b also 15 transmits SRS at the beginning of each slot. In this connection, one of two SRSs is transmitted from the transmitting and receiving antenna 110 and the other is transmitted from the transmitting and receiving antenna .110b. That is, the mobile station 100b is 20 designed to transmit the SRS from the transmitting and receiving antenn 110b even while transmitting ACK from the transmitting and receiving antenna 110. This enables the base station. 200a to measure the communication qualities of both the transmitting and receiving antennas 25 100 and 100b. FIG. 18 illustrates an example of uplink signals including CQI according to the third embodiment. FIG. 18 6072332-1 -45 illustrates how to allocate radio resources in the case where a signal ir icating CQI and SRS are multiplexed in a subframe with Short CP. The mobile station 100b transmits CQI and RS 5 signals on an uplink control channel j from the transmitting and receiving antenna 110. The mobile station 100b als6 transmits SRS at the beginning of each slot. In this connection, one of two SRSs is transmitted from the- transmitting and receiving antenna 110 while the 10 other is transmitted from the transmitting and receiving antenna 110b. ,That is, the mobile station 100b is designed to transmit the SRS from the transmitting and receiving antenna -110b even while transmitting CQI from the transmitting and receiving antenna 110. This allows 15 the base station 200a to measure the communication qualities of both the transmitting and receiving antennas 110 and 110b. Bf the way, only for the mobile station 100b to select an antenna to be used, there is no need to measure 20 the communication.. quality of a wide range of frequencies. Further, if the mobile station 100b has no packet data to transmit on the uplink within a predetermined period of time, the base station 200a has no need to measure the communication quality of frequencies which may be used for 25 an uplink data channel. Therefore, as long as there is no packet data to be transmitted on the uplink, the mobile station "100b omits the SRS transmission at frequencies 6072332-1 .
-46 other than the frequency band of the uplink control channel. FIG. 19 illustrates another example of uplink signals including ACK according to the third embodiment. 5 FIG. 19 illustrates how to allocate radio resources in the case where a signal indicating ACK and SRS are multiplexed in a subframe with Short CP and the mobile station 100b has no packet data to transmit. The mobile station 100b transmits ACK and RS 10 signals on they uplink control channel j from the transmitting and receiving antenna 110. The mobile station -100b also transmits SRS with only the frequency band of the uplink control channel j at the beginning of each slot. In this connection, the SRS transmission is 15 made from the transmitting and receiving antenna 110 in one of the two slots and from the transmitting and receiving antenna 110b in the other slot. This prevents the base station 200a from obtaining information to be used for selecting a frequency band to 20 be allocated for an uplink data channel, but enables the base sta-tion 200a to obtain information to be used by the mobile station 100b to select an antenna to be used. In order to omit the SRS transmission using the frequencies other than the frequency band of the uplink control 25 channel, the mobile station 100b gives the base station 200a an advance notice that the mobile station 100b has no packet data to transmit. 6072332-1 -47 FIG. 20 illustrates another example of uplink signals ,.ncluding CQI according to the third embodiment. FIG. 20 illustrates how to allocate radio resources in the case where a signal indicating CQI and SRS are multiplexed 5 in a subframe with Short CP and the mobile station 100b has no packet data to transmit. The mobile station 100b transmits CQI and RS signals on the uplink control channel j from the transmitting andt receiving antenna 110. The mobile 10 station 100b also transmits SRS with only the frequency band of the uplink control channel j at the beginning of each slot. In this connection, the SRS transmission is made from the transmitting and receiving antenna 110 in one of the two slots and from the transmitting and 15 receiving antenna 1.10b in the other slot. This prevents the base station 200a from obtaining information to be used for selecting a frequency band to be allocated for!an uplink data channel, but enables the base station 200a to obtain information to be used by the 20 mobile station 100b to select an antenna to be used. FIGS. 17 to 20 illustrate how ACK or CQI, as an example of an. uplink signal, is transmitted, and other types of control information can be transmitted in the same way. In addition, not only one type of control 25 information but also some types of control information can be transmitted in a same subframe. For example, ACK and CQI can be transmitted in a same subframe. In addition, 607233-2-14 -48 though FIGS. 17 to 20 illustrate the example of Short CP, Long CP may be used as described in the first embodiment. Further, SRS may, be transmitted in the first symbols of two consecutive subframes as described in the second 5 embodiment. Such the communication system can provide the same effects as that of the first embodiment. Further, with the communication system according to the third embodiment, the results of measuring communication quality based on 10 SRSs ~can be used for selecting an antenna in antenna diversity. Still further, when a mobile station has no packet data to transmit, a frequency band can be reduced for SRS transmission, thereby reducing the loads of measuring communication quality on the base station. 15 Although this embodiment uses the first symbol of each slot for SRS transmission, a predetermined symbol other than the first one can be used for the SRS transmission. Further, although this embodiment transmits a pair o'f SRSs in two consecutive slots or subframes, the 20 SRSs can be transmitted in separate slots or subframes. Still further, this embodiment uses the two limiting frequencies of a frequency band available between the mobile station and base station for two uplink control channels, a predetermined frequency band other than the 25 limiting frequencies can be used. The foregoing is considered as illustrative only of the principles of the present invention. Further, since 6072332-1 -49 numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and applications shown and described, and accordingly, all suitable modifications 5 and equivalents may be regarded as falling within the scope of the invention in the appended claims and their equivalents. Description of Reference Numerals 1 Transmitting apparatus 10 la Transmiter 2 Receiving apparatus 2a Quality measuring unit 6072332-1