Abstract:
A mobile station apparatus in a CDMA/TDD mobile communication system employs a communication frame including a plurality of time slots. The time slots include a plurality of forward link time slots, disposed at regular intervals in the communication frame and assigned a common control channel. The time slots further include time slots other than the plurality of forward link time slots, divided into reverse link time slots and forward link time slots according to an amount of information on a forward link and on a reverse link. The mobile station apparatus includes a receiver that receives the communication frame including the plurality of time slots. A measurer measures individual reception qualities of the plurality of forward link time slots in the received communication frame including the forward link time slots assigned the common control channel. A weighter assigns a weight to each measured reception quality of the plurality of forward time slots. A transmission power controller performs transmission power control for reverse link time slots according to individual reception qualities of weighted forward link time slots.

Description:
CROSS-REFERENCE TO RELATED APPLICATION  
       [0001]     This application is a continuation of U.S. patent application Ser. No. 10/166,268 filed on Jun. 11, 2002, which is a divisional of U.S. patent application Ser. No. 09/264,826, filed on Mar. 9, 1999, the contents of both being hereby incorporated herein by reference in their entireties. 
     
    
     BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to a CDMA/TDD mobile communication system and method applying a same band transmission/reception system for assigning time slots at the same radio frequency band to communicate over a reverse link and a forward link alternately.  
         [0004]     2. Description of the Invention  
         [0005]     Conventionally, as a mobile communication system using a CDMA (Code Division Multiple Access) system, a W-CDMA (Wideband CDMA) system using a DS (Direct Sequence) system is known. The W-CDMA system uses a FDD (Frequency Division Duplex) system as a duplex system.  
         [0006]     As a duplex system, a TDD (Time Division Duplex) system is known other than the FDD. The TDD system uses a same band transmission/reception system for assigning time slots at the same radio frequency band to communicate a reverse link and a forward link alternately, which is also called Ping-Pong system.  
         [0007]     In addition, a multiple access system is a line connection system over which a plurality of stations concurrently communicate at the same frequency band. The CDMA system employs a technique for performing a multiple access by a spread spectrum communication in which information signals are spread by a spreading code to transmit over a spread band. In the DS system, information signals are multiplied by a spreading code in spreading.  
         [0008]     In the DS-CDMA system, since a plurality of communication links share the same frequency band, there is a problem to control each communication wave level at a reception to be equal (near-far problem). In other words, the conquest over this problem is necessary to achieve the CDMA communication system.  
         [0009]     The near-far problem is severer at a reception of a base station for concurrently receiving radio signals transmitted from a plurality of mobile stations (mobile radio terminal devices) each locating at a different place. Therefore, it is mandatory at the mobile station propagation path condition.  
         [0010]     In the TDD system, propagation path conditions such as fading correlate when intervals of forward and reverse links are short enough because the same frequency band is used for the forward and reverse links. It is thereby possible to perform a transmission power control by open-loop control.  
         [0011]     Some of such CDMA mobile communication system comprises a TDD configuration for dividing a communication frame into a plurality of time slots to assign each of traffic channel and control channel to a time slot to communicate over a plurality of links.  
         [0012]      FIG. 1  illustrates a frame diagram in a conventional CDMA/TDD mobile communication system.  
         [0013]      FIG. 1  illustrates an example where one frame  1  is divided into eight time slots  0  to  7 , time slots  0  to  3  are assigned to a forward link and time slots  4  to  7  are assigned to a reverse link.  
         [0014]     In forward link  2  toward a mobile station (not shown) from a base station (not shown), common control channel  3  such as synchronization control channel, a dedicated control channel and user information channel  4  that are transmitted between the base station and a dedicated mobile station are multiplexed. In reverse link  5  toward the base station from the mobile station, the dedicated control channel and user information channel  6  are multiplexed.  
         [0015]     The mobile station starts receiving when it is turned on, and acquires synchronization with the base station by detecting the synchronization control channel of common control channel  3  in forward link  2 . Then the mobile station performs a line connection via the dedicated control channel to start communicating with user information channel  4 . At this point, the mobile station measures reception quality of an assigned forward link time slot, and based on the measurement result, performs a transmission power control of an assigned reverse link time slot.  
         [0016]     However, in the conventional CDMA/TDD mobile communication system described above, when an assignment of time slots to forward link and reverse link is changed corresponding to information volume of the forward and reverse links, a configuration of the synchronization control channel becomes irregular. It thereby takes a longer time for a mobile station to acquire synchronization with a base station when it is turned on.  
         [0017]     In addition, in each communication link, since an interval of the assigned forward link time slot and the assigned reverse link time slot is long, the propagation path conditions of the forward and reverse links do not correlate so much, thereby decreasing an effect of an open-loop controlled transmission power control.  
       SUMMARY OF THE INVENTION  
       [0018]     It is an object of the present invention to provide a CDMA/TDD mobile communication system and method for enabling a synchronization acquisition time with a base station at a mobile station to be shortened, and enabling open-loop controlled transmission power control to function effectively when an assignment of time slots to forward and reverse links is changed corresponding to an information volume in the case where the information volumes of the forward and reverse links are asymmetry.  
         [0019]     The object is achieved by a CDMA/TDD mobile communication system comprising a base station apparatus having a control section for assigning one or more fixed forward link time slots to a plurality of time slots divided at a communication frame at a predetermined interval, while assigning forward link time slots and reverse link time slots to the time slots except for the fixed forward link time slots by allocating the time slots corresponding to a ratio of a total information volume of a forward link to a total information volume of a reverse link in the system, in order to transmit a control channel signal including a synchronization control channel signal using the fixed forward link time slots, and to transmit a traffic channel signal of the forward link and a traffic channel signal of the reverse link respectively using the forward link time slots and the reverse link time slots that are allocated according to the number of time slots respectively required corresponding to the respective information volume. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1  is a frame diagram applied in a conventional CDMA/TDD mobile communication system;  
         [0021]      FIG. 2  is block diagram of a base station in a CDMA/TDD mobile communication system according to a first embodiment of the present invention;  
         [0022]      FIG. 3  is a frame diagram illustrating an assignment of time slots at a communication frame applied in the CDMA/TDD mobile communication system according to the first embodiment of the present invention;  
         [0023]      FIG. 4  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to a second embodiment of the present invention;  
         [0024]      FIG. 5  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to a third embodiment of the present invention;  
         [0025]      FIG. 6  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to a fourth embodiment of the present invention;  
         [0026]      FIG. 7  is a block diagram of a mobile station in a CDMA/TDD mobile communication system according to a fifth embodiment of the present invention;  
         [0027]      FIG. 8  is an integration result diagram obtained by the mobile station according to the fifth embodiment integrating correlation value of a received signal with a spreading code of a forward synchronization control channel at each sampling timing over four time slots interval starting from an arbitrary time.  
         [0028]      FIG. 9  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to a sixth embodiment of the present invention; and  
         [0029]      FIG. 10  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to a seventh embodiment of the present invention.  
     
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS  
       [0030]     A CDMA/TDD mobile communication system and method according to the embodiments of the present invention are specifically explained below with reference to attached drawings.  
         [heading-0031]     (First Embodiment)  
         [0032]      FIG. 2  is block diagram of a base station in a CDMA/TDD mobile communication system according to the first embodiment of the present invention.  
         [0033]     Base station  100  illustrated in  FIG. 2  is composed of coding section  104  having first coding section  101 , second coding section  102  and third coding section  103 , spreading section  108  having first spreading section  105 , second spreading section  106  and third spreading section  107 , multiplexing section  109 , D/A conversion section  110 , transmission frequency conversion section  111 , reception frequency conversion section  112 , A/D conversion section  113 , allocating section  114 , correlation detection section  118  having first correlation detection section  115 , second correlation detection section  116 , and third correlation detection section  117 , decoding section  122  having first decoding section  119 , second decoding section  120  and third decoding section  121 , transmission/reception antenna  123 , transmission/reception switching section  124  and control section  125 .  
         [0034]     Coding sections  101  to  103  execute coding of first to third forward link dedicated control channel signals  131 ,  132  and  133  respectively. Spreading sections  105  to  107  executed spreading the coded channel signals  134 ,  135  and  136  respectively.  
         [0035]     Multiplexing section  109  multiplexes the spread channel signals  137  to  139 . D/A conversion section  110  converts the multiplexed signal  140  into analogue signal  141 . Transmission frequency conversion section  111  converts the analogue signal  141  into transmission signal  142  with radio frequency.  
         [0036]     Transmission/reception switching section  124  switches transmission/reception antenna  123  for a transmission site and a transmission site to connect. The transmission signal  142  is transmitted from transmission/reception antenna through transmission/reception switching section  124  to a mobile station (not shown).  
         [0037]     The reception frequency conversion section  112  converts received signal  431  with radio frequency into signal  144  with baseband frequency. The received signal  431  is received at transmission/reception antenna  123  and transmitted through transmission/reception switching section  124  to the section  112 .  
         [0038]     A/D conversion section  113  converts the signal  144  with baseband frequency into digital received signal  145 . Allocating section  114  allocates digital received signal  145  to channel signals  146 ,  147  and  148 .  
         [0039]     Correlation detection sections  115  to  117  detect correlation of reverse link common dedicated channel signals  146  to  148  respectively. Decoding sections  119  to  121  decode correlation detection channel signals  149 ,  150  and  151  to output channel decoded signals  152 ,  153  and  154 . Control section  125  controls over each section described above.  
         [0040]     In a configuration described above, forward link common channel (such as synchronization control channel) signals  131  to  133  are coded and constructed into frames at coding sections  101  to  103  and output to spreading sections  105  to  107  respectively. The coding may be an error correction coding, and in this case, interleaving processing is also executed.  
         [0041]     Spreading sections  105  to  107  respectively spread coded channel signals  134  to  136  with a spreading code to output spread signals  137  to  139  to multiplexing section  109 . The spreading code may be assigned from control section  125 .  
         [0042]     Multiplexing section  109  provides spread signals  137  to  139  at time slots to multiplex according to an instruction from control section  125 . At this stage, channel signals provided at the same time slot are multiplexed. In the case where the multiplexing processing is executed, a transmission power control may be performed to control an amplitude of each of channel spread signals  137  to  139 .  
         [0043]     Digital multiplexed signal  140  is converted into analogue signal  141  in D/A conversion section  110 . The analogue signal  141  is converted into transmission signal  142  with radio frequency in transmission frequency conversion section  111 . The transmission signal  142  is transmitted from transmission/reception antenna  123  through transmission/reception switching section  124 .  
         [0044]     At this stage, transmission/reception switching section  124  connects transmission/reception antenna  123  to transmission frequency conversion section  111  for a forward link time slot and to reception frequency conversion section  112  for a reverse link time slot according to an instruction from control section  125 .  
         [0045]     On the other hand, reception signal  143 , which is received at transmission/reception antenna  123  from a mobile station, is input to reception frequency conversion section  112  through transmission/reception switching section  124 . Reception frequency conversion section  112  converts the received signal  143  with radio frequency into signal  144  with baseband frequency.  
         [0046]     A/D conversion section  113  converts the analogue signal  144  with baseband frequency into digital signal  145  to output to allocating section  114 . Allocating section  114  divides the digital signal  145  into reverse common control channel signals  146  to  148  according to an instruction of control section  125  to output to correlation detection sections  115  to  117  respectively.  
         [0047]     Correlation detection sections  115  to  117  despread the reverse common control channel signals  146  to  148  to detect correlation of a received signal with a spreading code. Each spreading code may be instructed by control section  125 .  
         [0048]     Detected correlation values (correlation signals)  149  to  151  are respectively output to decoding sections  119  to  121 , which decode reverse common control channel signals based on correlation values  149  to  151 . At this stage, when a mobile station executes an error correction coding for a reverse link, an error correction decoding with deinterleaving processing is executed.  
         [0049]     In addition, each common section may be provided to use for all channels according to time slots instead of using coding sections  101  to  103 , spreading sections  105  to  107 , correlation detection sections  115  to  117 , and decoding sections  119  to  121 .  
         [0050]     An assignment control of time slots is explained from among controls executed by control section  125  with reference to  FIG. 3 .  FIG. 3  is a frame diagram illustrating an assignment of time slots at a communication frame in a CDMA/TDD mobile communication system. The assignment illustrates an example where one frame  201  is divided into 16 time slots  0  to  15 .  
         [0051]     In  FIG. 3, 202  indicates a time slot at which a forward link common control channel signal and a forward link user information channel signal are provided,  203  indicates a time slot at which only a forward link user information channel signal is provided, and  204  indicates a time slot at which a reverse link channel signal is provided.  
         [0052]     Control section  125  first compares an information volume of the forward link with that of reverse link and determines the numbers of time slots to be assigned to the forward link and the reverse link. At this point, the number of time slots necessary to transmit a forward link common control channel signal including a synchronization control channel signal is primarily assigned to the forward link. The other time slots are assigned to the forward link and reverse link taking the information volumes into consideration.  
         [0053]     Then, the forward link common control channel signal including the synchronization control channel signal is provided at a time slot at a predetermined time slots interval at a frame, accordingly the time slot is assigned for a forward link time slot.  
         [0054]     Further, the rest of forward link time slots are provided at the frame. At this point, the forward link time slots are provided primarily at time slots except for those following just after the forward link time slots to transmit control channel signals including synchronization control channel signals. Then the other time slots are assigned for the reverse link time slots.  
         [0055]     In the forward link time slots at which forward link common control channel signals including synchronization control channel signals are provided, the forward link common control channel signals may be not only provided, but also other forward link channel signals may be provided. In this case, a plurality of channel signals provided in the time slot are multiplexed to transmit.  
         [0056]      FIG. 3  illustrates examples of assigning sixteen time slots at a frame.  
         [0057]     (A) in  FIG. 3  illustrates the case where four time slots  0 ,  4 ,  8  and  12  are assigned for forward link time slots, and the other twelve time slots are assigned for reverse link time slots.  
         [0058]     (B) in  FIG. 3  illustrates the case where eight time slots are assigned for forward link time slots, and the other eight time slots are assigned for reverse link time slots. The times slots  0 ,  4 ,  8  and  12  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals and the time slots  2 ,  6 ,  10  and  14  are further assigned for forward link time slots. The time slots  1 ,  3 ,  5 ,  7 ,  9 ,  11 ,  13  and  15  are assigned for reverse link time slots.  
         [0059]     (C) in  FIG. 3  illustrates the case where twelve time slots are assigned for forward link time slots, and the other four time slots are assigned for reverse link time slots. The time slots  0 ,  4 ,  8  and  12  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals and the time slots  2 ,  3 ,  6 ,  7 ,  10 ,  11 ,  14  and  15  are further assigned for forward link time slots. The time slots  1 ,  5 ,  9 , and  13  are assigned for reverse link time slots.  
         [0060]     (D) in  FIG. 3  illustrates the case where fifteen time slots are assigned for forward link time slots, and the other one time slot is assigned for a reverse link time slot. The time slots  0 ,  4 ,  8  and  12  are assigned for the forward link time slots to transmit forward link common control channel signals including synchronization control channel signals and the time slots  2 ,  3 ,  5 ,  6 ,  7 ,  9 ,  10 ,  11 ,  13 ,  14  and  15  are further assigned for forward link time slots. The time slot  1  is assigned for the reverse link time slot.  
         [0061]     In (c) and (D) in  FIG. 3 , the reverse link time slots are positioned just after the time slots assigned for forward link time slots to transmit common control channel signals including synchronization control channel signals. As a result, in the case where a closed-loop control is performed in the system, it is possible for a mobile station to control transmission power using a TPC bit contained in the control channel signal in the received forward link common control channel signal. Accordingly, the mobile station can respond rapidly to a propagation environment such as fading.  
         [0062]     The assignment of time slots may be changed manually corresponding to a change of an information volume, or changed automatically according to the change of the information volume caused by a new connection or a break, or at predetermined intervals.  
         [0063]     A mobile station acquires synchronization with a base station when it is turned on by first despreading a received signal with a spreading code used in the synchronization control channel signal to detect the synchronization control channel signal.  
         [0064]     Under such condition, the mobile station does not know an assignment of time slots for a forward link and a reverse link when it is turned on, however knows in advance that a synchronization control channel signal is positioned once every four slots with three time slots inserted. Therefore, the mobile station can detect a timing of the synchronization control channel signal by integrating correlation values over every four time slots interval.  
         [0065]     The mobile station decodes the common control channel signal including the synchronization control channel signal using the detected timing in order to recognize positions of forward link time slots and reverse link time slots and time slots assigned to each channel.  
         [0066]     Then the mobile station performs connection processing using the recognized common control channel and dedicated control channel to establish a user information channel. Signals of user information channel between a mobile station and a base station are provided differently for a forward link and a reverse link at a frame  201 . Therefore, the time difference between a forward link user information channel time slot and a reverse link user information channel time slot is sometimes large with the other many time slots inserted between those time slots.  
         [0067]     In the case of performing a reverse link transmission power control using an open-loop control, since the correlation characteristic of propagation path conditions of a forward link and a reverse link is used, the large time difference introduces the low correlation characteristic, resulting in a reduced accuracy of the transmission power control.  
         [0068]     However, since the forward link common control channel signal is transmitted every four time slots, when a reception quality is measured using the forward link common control channel signal and the transmission power control is performed based on the measured reception quality, the time difference between the forward link time slot used to measure the reception quality and the reverse link time slot to be transmitted under the transmission power control are a two time slots time at maximum, thereby enabling an efficient transmission power control.  
         [0069]     In addition, It is preferable to use the arbitrary number of time slots composing a frame other than sixteen. It is also preferable to provide a forward link common control channel signal every arbitrary number of time slots other than every four time slots. It is further preferable to provide a forward link common control channel signal at a predetermined periodical pattern other than at equal intervals.  
         [0070]     As described above, according to the first embodiment, under the control of control section  125  in base station  100 , some of time slots at a communication frame are assigned primarily to fixed forward link time slots at predetermined intervals and the other time slots are allocated to forward link time slots and reverse link time slots corresponding to a ratio of the total information volume of the reverse link to that of the forward link in a system, in order to transmit a control channel signal including a synchronization control channel signal using the fixed forward link time slot and transmit traffic channel signals of forward link and reverse link respectively using the forward link time slots and the reverse link time slots that are allocated according to the number of time slots respectively required corresponding to the respective information volume. The above processing makes it possible to shorten a time for a mobile station to acquire synchronization with a base station even when an assignment of time slots for forward and reverse links is changed corresponding to the information volumes of forward link and reverse link in the case where the information volumes are asymmetry, thereby enabling an open-loop controlled transmission power control to function effectively.  
         [heading-0071]     (Second Embodiment)  
         [0072]      FIG. 4  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to the second embodiment of the present invention.  
         [0073]      FIG. 4  illustrates an example where one frame  301  is divided into sixteen time slots  0  to  15 . In  FIG. 4 , the reference number  302  indicates a time slot at which a forward link common control channel signal and a forward link user information channel signal are provided, the reference number  303  indicate a time slot at which only a forward link user information channel signal is provided, and the reference number  304  indicate a time slot at which a reverse link channel signal is provided.  
         [0074]     Control section  125  of base station  100  illustrated in  FIG. 2  first compares an information volume of the forward link with that of reverse link and determines the numbers of time slots to be assigned to the forward link and the reverse link.  
         [0075]     At this point, the number of time slots necessary to transmit a forward link common control channel signal including a synchronization control channel signal is primarily assigned to the forward link. The other time slots are assigned to the forward link and reverse link taking the information volumes into consideration.  
         [0076]     Then, the forward link common control channel signal including the synchronization control channel signal is provided at a slot every two slots with a slot inserted, accordingly the time slot is assigned for a forward link time slot. Further, the other forward link time slots are provided at the frame, and the rest of the time slots are assigned for reverse link time slots.  
         [0077]     In the forward link time slots at which forward link common control channel signals including synchronization control channel signals are provided, the forward link common control channel signals including synchronization control channel signals may be not only provided, but also other forward link channel signals may be provided. In this case, a plurality of channel signals provided in the same time slot are multiplexed to transmit.  
         [0078]     (A) in  FIG. 4  illustrates the case where eight time slots are assigned for forward link time slots, and the other eight time slots are assigned for reverse link time slots. The time slots  0 ,  2 ,  4 ,  6 ,  8 ,  10 ,  12  and  14  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals, and the time slots  1 ,  3 ,  5 ,  7 ,  9 ,  11 ,  13  and  15  are assigned for reverse link time slots.  
         [0079]     (B) in  FIG. 4  illustrates the case where twelve time slots are assigned for forward link time slots, and the other eight time slots are assigned for reverse link time slots. The time slots  0 ,  2 ,  4 ,  6 ,  8 ,  10 ,  12  and  14  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals and the time slots  1 ,  5 ,  9  and  13  are further assigned for forward link time slots. The time slots  3 ,  7 ,  11 , and  15  are assigned for reverse link time slots.  
         [0080]     (C) in  FIG. 4  illustrates the case where fourteen time slots are assigned for forward link time slots, and the other two time slots are assigned for reverse link time slots. The time slots  0 ,  2 ,  4 ,  6 ,  8 ,  10 ,  12  and  14  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals and the time slots  1 ,  3 ,  5 ,  9 ,  11  and  13  are further assigned for forward link time slots. The time slots  7  and  15  are assigned for reverse link time slots.  
         [0081]     (D) in  FIG. 3  illustrates the case where fifteen time slots are assigned for forward link time slots, and the other one slot is assigned for a reverse link time slot. The time slots  0 ,  2 ,  4 ,  6 ,  8 ,  10 ,  12  and  14  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals and the time slots  1 ,  3 ,  5 ,  7 ,  9 ,  11  and  13  are further assigned for forward link time slots. The time slot  15  is assigned for a reverse link time slot.  
         [0082]     As describe above, in  FIG. 4 , time slots provided just after time slots to transmit forward link common control channel signals including synchronization control channel signals are always reverse link time slots.  
         [0083]     In other words, by providing one of time slots to transmit forward link common control channel signals including synchronization control channel signals every two time slots, i.e., with one other time slot inserted between those, even when reverse time slots are provided in any time slots, it is configured that the time slots just before the reverse link time slots are always the forward link time slots to transmit common control channel signals including synchronization control channel signals.  
         [0084]     Therefore, in the case where a closed-loop control is performed in the system, it is possible for a mobile station to control transmission power using a TPC bit contained in the control channel signal in the received forward link common control channel signal. Accordingly, the mobile station can respond rapidly to a propagation environment such as fading.  
         [0085]     The assignment of time slots may be changed manually corresponding to a change of an information volume, or changed automatically according to the change of the information volume caused by a new connection or a break, or at predetermined intervals.  
         [0086]     Under such condition, a mobile station (not shown) acquires synchronization with a base station when it is turned on by first despreading a received signal with a spreading code used in the synchronization control channel signal to detect the synchronization control channel signal.  
         [0087]     The mobile station does not know an assignment of time slots for a forward link and a reverse link when it is turned on, however the mobile station can detect a timing of the synchronization control channel signal by integrating correlation values over every two time slots interval.  
         [0088]     Then, the mobile station decodes the common control channel signal including the synchronization control channel signal using the detected timing in order to recognize positions of forward link time slots and reverse link time slots and time slots assigned to each channel, and performs connection processing using the recognized common control channel and dedicated control channel to establish a user information channel.  
         [0089]     User information channel slots between a mobile station and a base station are positioned differently for forward link and reverse link at a frame. Therefore, the time difference between a forward link user information channel time slot and a reverse link user information channel time slot is sometimes large with the other many time slots inserted between those time slots.  
         [0090]     In the case of performing a reverse link transmission power control using an open-loop control, the large time difference introduces the low correlation characteristic of propagation path conditions of the forward link and reverse link, resulting in a reduced accuracy of the transmission power control. However, since the common control channel is transmitted once every two slots, when the transmission power control is performed based on the reception quality obtained by using the received common control channel, it is possible to use the reception quality of the forward link time slot just before the reverse link time slot to be transmitted under the transmission power control, thereby enabling an effective transmission power control. In addition, it is also preferable to use the arbitrary number of time slots composing a frame other than sixteen.  
         [0091]     As described above, according to the second embodiment, a time slot in every two slots is assigned for a fixed forward link time slot and the other time slots are allocated for forward link time slots and reverse link time slots corresponding to a ratio of the total information volume of forward link to that of the reverse link in a system, in order to transmit a control channel signal including a synchronization control channel signal using the fixed forward link time slot and transmit traffic channel signals of forward link and reverse link respectively using the forward link time slots and the reverse link time slots that are allocated according to the number of time slots respectively required corresponding to the respective information volume. The above processing makes it possible to shorten a time for a mobile station to acquire synchronization with a base station even when an assignment of time slots for forward and reverse links is changed corresponding to the information volumes of forward link and reverse link when the information volumes are asymmetry, thereby enabling an open-loop controlled transmission power control to function effectively.  
         [heading-0092]     (Third Embodiment)  
         [0093]      FIG. 5  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to the third embodiment of the present invention.  
         [0094]      FIG. 5  illustrates an example where one frame  401  is divided into sixteen time slots  0  to  15 . In  FIG. 5 , the reference number  402  indicates a time slot at which a forward link common control channel signal and a forward link user information channel signal are provided, the reference number  403  indicates a time slot at which a forward link user information channel signal is provided, and the reference number  404  indicates a time slot at which a reverse link channel signal is provided.  
         [0095]     Control section  125  of base station  100  illustrated in  FIG. 2  first compares an information volume of the forward link with that of reverse link and determines the numbers of time slots to be assigned to the forward link and the reverse link.  
         [0096]     At this point, the number of time slots necessary to transmit a forward link common control channel signal including a synchronization control channel signal is primarily assigned to the forward link. The other time slots are assigned to the forward link and reverse link taking the information volumes into consideration.  
         [0097]     Then, the forward link common control channel signal including the synchronization control channel signal is provided at a slot every eight time slots with seven time slots inserted, accordingly the time slot is assigned for a forward link time slot. Further, the other forward link time slots are provided at the frame, and the rest of time slots are assigned for reverse link time slots.  
         [0098]     In the forward link time slots at which forward link common control channel signals including synchronization control channel signals are provided, the forward link common control channel signals including synchronization control channel signals may be not only provided, but also other forward link channel signals may be provided. In this case, a plurality of channel signals provided in the same time slot are multiplexed to transmit. (A) in  FIG. 5  illustrates the case where two time slots are assigned for forward link time slots, and the other fourteen time slots are assigned for reverse link time slots. The time slots  0  and  8  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals. The other time slots  1  to  7  and  9  to  15  are assigned for reverse link time slots. (B) in  FIG. 5  illustrates the case where eight time slots are assigned for forward link time slots, and the other eight time slots are assigned for reverse link time slots. The time slots  0  and  8  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals and the time slots  2 ,  4 ,  6 ,  10 ,  12  and  14  are further assigned for forward link time slots. The time slots  1 ,  3 ,  5 ,  7 ,  9 ,  11 ,  13  and  15  are assigned for reverse link time slots.  
         [0099]     (C) in  FIG. 5  illustrates the case where twelve time slots are assigned for forward link time slots, and the other four time slots are assigned for reverse link time slots. The time slots  0  and  8  are assigned for forward link time slots to transmit forward link common control channel signals including synchronization control channel signals and the time slots  2 ,  3 ,  4 ,  6 ,  7 ,  10 ,  11 ,  12 ,  14  and  15  are further assigned for forward link time slots. The time slots  1 ,  5 ,  9  and  13  are assigned for reverse link time slots.  
         [0100]     (D) in  FIG. 5  illustrates the case where fifteen time slots are assigned for forward link time slots, and the other one time slot is assigned for a reverse link time slot. The time slots  0  and  8  are assigned for forward link time slots to transmit forward common control channel signals including synchronization control channel signals and the time slots  2  to  7  and  9  to  15  are further assigned for forward link time slots. The other time slot  15  is assigned for a reverse link time slot.  
         [0101]     As describe above, in  FIG. 5 , time slots provided just after time slots to transmit forward link common control channel signals including synchronization control channel signals are always reverse link time slots.  
         [0102]     In other words, by providing one of time slots to transmit forward link common control channel signals including synchronization control channel signals every eight time slots, i.e., with seven other time slots inserted between those, even though reverse time slots are provided at any time slots, it is configured that the time slot just before at least one of the reverse link time slots at a frame is always a forward link-time slot to transmit common control channel signals including synchronization control channel signals.  
         [0103]     Therefore, in the case where a closed-loop control is performed in the system, it is possible for a mobile station to control transmission power using a TPC bit contained in the control channel signal in the received forward link common control channel signal. Accordingly, the mobile station can respond rapidly to a propagation environment such as fading.  
         [0104]     The assignment of time slots may be changed manually corresponding to a change of an information volume, or changed automatically according to the change of the information volume caused by a new connection or a break, or at predetermined intervals.  
         [0105]     Under such condition, a mobile station (not shown) acquires synchronization with a base station when it is turned on by first despreading a received signal with a spreading code used in the synchronization control channel signal to detect the synchronization control channel signal.  
         [0106]     The mobile station does not know an assignment of time slots for a forward link and a reverse link when it is turned on, however the mobile station can detect a timing of the synchronization control channel signal by integrating correlation values over every eight time slots intervals.  
         [0107]     Then, the mobile station decodes the common control channel signal including the synchronization control channel signal using the detected timing in order to recognize positions of forward link time slots and reverse link time slots and time slots assigned to each channel, and performs connection processing using the recognized common control channel and dedicated control channel to establish a user information channel.  
         [0108]     User information channel slots between a mobile station and a base station are positioned differently for forward link and reverse link at a frame. Therefore, the time difference between a forward link user information channel time slot and a reverse link user information channel time slot is sometimes large with the other many time slots inserted between those time slots.  
         [0109]     In the case of performing a reverse link transmission power control using an open-loop control, the large time difference introduces the low correlation characteristic of propagation path conditions of the forward link and reverse link, resulting in a reduced accuracy of the transmission power control. However, since the common control channel is transmitted once every eight slots, when the transmission power control is performed based on the reception quality obtained by using the received common control channel, it is possible to use the reception quality of the forward link time slot just before the reverse link time slot to be transmitted under the transmission power control, thereby enabling an effective transmission power control. In addition, it is also preferable to use the arbitrary number of time slots composing a frame other than sixteen.  
         [0110]     As described above, according to the third embodiment, a time slot in every eight slots is assigned for a fixed forward link time slot and the other time slots are allocated for forward link time slots and reverse link time slots corresponding to a ratio of the total information volume of reverse link to that of the forward link in a system, in order to transmit a control channel signal including a synchronization control channel signal using the fixed forward link time slot and transmit traffic channel signals of forward link and reverse link respectively using the forward link time slots and the reverse link time slots that are allocated according to the number of time slots respectively required corresponding to the respective information volume. The above processing makes it possible to shorten a time for a mobile station to acquire synchronization with a base station even when an assignment of time slots for forward and reverse links is changed corresponding to the information volumes of forward link and reverse link in the case where the information volumes are asymmetry, thereby enabling an open-loop controlled transmission power control to function effectively. In this case, it is possible to obtain many variations of allocation configuration of the number of forward link time slots and the number of reverse link time slots.  
         [heading-0111]     (Fourth Embodiment)  
         [0112]      FIG. 6  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to the fourth embodiment of the present invention.  
         [0113]      FIG. 6  illustrates an example where one frame  501  is divided into sixteen time slots  0  to  15 . In  FIG. 6 , the reference number  502  indicates a time slot at which a forward link common control channel signal and a forward link user information channel signal are provided, the reference number  503  indicates a time slot at which a forward link user information channel signal is provided, and the reference number  504  indicates a time slot at which a reverse link channel signal is provided.  
         [0114]     Control section  125  of base station  100  illustrated in  FIG. 2  first compares an information volume of the forward link with that of reverse link and determines the numbers of time slots to be assigned to the forward link and the reverse link.  
         [0115]     At this point, the number of time slots necessary to transmit a forward link common control channel signal including a synchronization control channel signal is primarily assigned to the forward link. The other time slots are assigned to the forward link and reverse link taking the information volumes into consideration.  
         [0116]     Then, the forward link common control channel signal including the synchronization control channel signal is provided at a slot in every sixteen slots, accordingly the time slot is assigned for a forward link time slot. Further, the other forward link time slots are provided at the frame, and the rest of time slots are assigned for reverse link time slots.  
         [0117]     In the forward link time slots at which forward link common control channel signals including synchronization control channel signals are provided, the forward link common control channel signals including synchronization control channel signals may be not only provided, but also other forward link channel signals may be provided. In this case, a plurality of channel signals provided in the time slot are multiplexed to transmit.  
         [0118]     (A) in  FIG. 6  illustrates the case where one time slot is assigned for a forward link time slot, and the other fifteen time slots are assigned for reverse link time slots. The time slot  0  is assigned for a forward link time slot to transmit forward link common control channel signals including synchronization control channel signals. The other time slots  1  to  15  are assigned for reverse link time slots.  
         [0119]     (B) in  FIG. 4  illustrates the case where eight time slots are assigned for forward link time slots, and the other eight time slots are assigned for reverse link time slots. The time slot  0  is assigned for a forward link time slot to transmit forward link common control channel signals including synchronization control channel signals and the time slots  2 ,  4 ,  6 ,  8 ,  10 ,  12  and  14  are further assigned for forward link time slots. The time slots  1 ,  3 ,  5 ,  7 ,  9 ,  11 ,  13  and  15  are assigned for reverse link time slots.  
         [0120]     (C) in  FIG. 6  illustrates the case where twelve time slots are assigned for forward link time slots, and the other four time slots are assigned for reverse link time slots. The time slot  0  is assigned for a forward link time slot to transmit common control channel signals including synchronization control channel signals and the time slots  2 ,  3 ,  4 ,  6 ,  7 ,  8 ,  10 ,  11 ,  12 ,  14  and  15  are further assigned for forward link time slots. The time slots  1 ,  5 ,  9  and  13  are assigned for reverse link time slots.  
         [0121]     (D) in  FIG. 3  illustrates the case where fifteen time slots are assigned for forward link time slots, and the other one time slot is assigned for reverse link time slots. The time slot  0  is assigned for a forward link time slot to transmit common control channel signals including synchronization control channel signals and the time slots  2  to  15  are further assigned for forward link time slots. The time slot  1  is assigned for a reverse link time slot.  
         [0122]     As describe above, in  FIG. 6 , time slots provided just after time slots to transmit forward link common control channel signals including synchronization control channel signals are always reverse link time slots.  
         [0123]     In other words, by providing one of time slots to transmit forward link common control channel signals including synchronization control channel signals every sixteen time slots, i.e., with fifteen other time slots inserted between those, even though reverse time slots are provided in any time slots, it is configured that the time slot just before at least one of the reverse link time slots at a frame is always a forward link time slot to transmit common control channel signals including synchronization control channel signals.  
         [0124]     Therefore, in the case where a closed-loop control is performed in the system, it is possible for a mobile station to control transmission power using a TPC bit contained in the control channel signal in the received forward link common control channel signal. Accordingly, the mobile station can respond rapidly to a propagation environment such as fading.  
         [0125]     The assignment of time slots may be changed manually corresponding to a change of an information volume, or changed automatically according to the change of the information volume caused by a new connection or a break, or at predetermined intervals.  
         [0126]     Under such condition, a mobile station (not shown) acquires synchronization with a base station when it is turned on by first despreading a received signal with a spreading code used in the synchronization control channel signal to detect the synchronization control channel signal.  
         [0127]     The mobile station does not know an assignment of time slots for a forward link and a reverse link when it is turned on, however the mobile station can detect a timing of the synchronization control channel signal by integrating correlation values over every fifteen time slots intervals.  
         [0128]     Then, the mobile station decodes the common control channel signal including the synchronization control channel signal using the detected timing in order to recognize positions of forward link time slots and reverse link time slots and time slots assigned to each channel, and performs connection processing using the recognized common control channel and dedicated control channel to establish a user information channel.  
         [0129]     User information channel slots between a mobile station and a base station are positioned differently for forward link and reverse link at a frame. Therefore, the time difference between a forward link user information channel time slot and a reverse link user information channel time slot is sometimes large with the other many time slots inserted between those time slots.  
         [0130]     In the case of performing a reverse link transmission power control using an open-loop control, the large time difference introduces the low correlation characteristic of propagation path conditions of the forward link and reverse link, resulting in a reduced accuracy of the transmission power control. However, since the common control channel is transmitted once every sixteen slots, when the transmission power control is performed based on the reception quality obtained by using the received common control channel, it is possible to use the reception quality of the forward link time slot just before the reverse link time slot to be transmitted under the transmission power control, thereby enabling an effective transmission power control. In addition, it is also preferable to use the arbitrary number of time slots composing a frame other than sixteen.  
         [0131]     As described above, according to the fifth embodiment, a time slot in every sixteen slots is assigned for a fixed forward link time slot and the other time slots are allocated for forward link time slots and reverse link time slots corresponding to a ratio of the total information volume of reverse link to that of the forward link in a system, in order to transmit a control channel signal including a synchronization control channel signal using the fixed forward link time slot and transmit traffic channel signals of forward link and reverse link respectively using the forward link time slots and the reverse link time slots that are allocated according to the number of time slots respectively required corresponding to the respective information volume. The above processing makes it possible to shorten a time for a mobile station to acquire synchronization with a base station even when an assignment of time slots for forward and reverse links is changed corresponding to the information volumes of forward link and reverse link in the case where the information volumes are asymmetry, thereby enabling an open-loop controlled transmission power control to function effectively. In this case, it is possible to obtain many variations of allocation configuration of the number of forward link time slots and the number of reverse link time slots.  
         [heading-0132]     (Fifth Embodiment)  
         [0133]      FIG. 7  is block diagram of a mobile station as an example of communication terminal devices in a CDMA/TDD mobile communication system according to the fifth embodiment of the present invention.  
         [0134]     Mobile station  600  illustrated in  FIG. 7  is composed of coding section  601 , spreading section  602 , amplifying section  603 , D/A conversion section  640 , transmission frequency conversion section  605 , reception frequency conversion section  606 , A/D conversion section  607 , allocating section  608 , correlation detection section  611  including first correlation detection section  609 , and second correlation detection section  610 , decoding section  614  including first decoding section  612  and second decoding section  613 , transmission/reception antenna  615 , transmission/reception switching section  616  and control section  617 .  
         [0135]     Coding section  601  codes reverse link channel signal  621 . Spreading section  602  spreads coded signal  622 . Amplifying section  603  amplifies spread signal  623 .  
         [0136]     D/A conversion section  604  converts digital amplified signal  624  into analogue signal  625 . Transmission frequency conversion section  605  converts the analogue signal  625  into transmission signal  626  with radio frequency.  
         [0137]     Transmission/reception switching section  616  switches transmission/reception antenna  615  for a transmission site and a transmission site to connect. The transmission signal  626  is transmitted from transmission/reception antenna  615  through transmission/reception switching section  616  to a base station illustrated in  FIG. 2  by radio communication.  
         [0138]     Reception frequency conversion section  606  converts received signal  627  with radio frequency into signal  628  with baseband frequency. The received signal  627  is received at transmission/reception antenna  615  and transmitted through transmission/reception switching section  616  to the section  606 .  
         [0139]     A/D conversion section  607  converts the signal  628  with baseband frequency into digital received signal  629 . Allocating section  608  allocates the digital received signal  629  to channel signals  630  and  631 .  
         [0140]     Correlation detection sections  609  and  610  detect respectively forward link common dedicated channel signals  630  and  631 . Decoding sections  612  and  613  decode channel correlation detection signals  632  and  633  to output channel decoded signals  634  and  635  respectively. Control section  617  controls over each section described above.  
         [0141]     In a configuration described above, reverse link channel signal  612  is coded and constructed into frames at coding section  602  and output to spreading section  602 . The coding may be an error correction coding, and in this case, interleaving processing is also executed.  
         [0142]     Spreading section  602  spreads coded signal  622  with a spreading code and outputs spread signal  623  to amplifying section  603 . The spreading code may be assigned from control section  617 .  
         [0143]     Amplifying section  603  provides the spread signal  623  at a time slot assigned according to an instruction from control section  617  and performs transmission power control by amplifying or decreasing an amplitude of the spread signal  623  according to an instruction from control section  617  to output to D/A conversion section  604 .  
         [0144]     D/A conversion section  604  converts digital amplified  624  into analogue signal  625  to output to transmission frequency conversion section  605 . Transmission frequency conversion section  605  converts the analogue signal  625  into transmission signal  626  with radio frequency to output to transmission/reception switching section  616 .  
         [0145]     Transmission/reception switching section  616  connects transmission/reception antenna  615  to transmission frequency conversion section  605  for a reverse link time slot and to reception frequency conversion section  606  for a forward link time slot according to an instruction from control section  617 .  
         [0146]     In other words, with respect to reverse link time slots, transmission signal  626 , which is subjected to the conversion of frequency into the radio frequency at reception frequency conversion section  605 , is transmitted from transmission/reception antenna  123  to a base station  100 .  
         [0147]     On the other hand, with respect to forward link time slots, received signal  627  that is received at transmission/reception antenna  123  is input to reception frequency conversion section  606 .  
         [0148]     Reception frequency conversion section  606  converts the received signal  627  with radio frequency into received signal  628  with baseband frequency to output to A/D conversion section  607 . A/D conversion section  607  converts the analogue signal  628  into digital signal  629  to output to allocating section  608 .  
         [0149]     Allocating section  608  divides digital signal  629  into signals  630  and  631  according to an instruction from control section  617  to output to correlation detection sections  609  and  610  respectively.  
         [0150]     Correlation detection sections  609  and  610  despread divided signals  630  and  631  respectively to detect correlation of a received signal with a spreading code and obtain correlation values  632  and  633  respectively. Each spreading code may be instructed from control section  125 . Detected correlation values  632  and  633  are respectively output to decoding sections  612  and  613 , while output to control section  617 .  
         [0151]     Decoding sections  612  and  613  decode forward common control channel signals  634  and  635  using correlation values  632  and  633 . At this point, when base station  100  executes an error correction coding for a forward link, an error correction decoding with deinterleaving processing is executed.  
         [0152]     In addition, each common section may be provided to use for all channels according to time slots instead of using correlation detection sections  609  and  610 , and decoding sections  612  and  613 .  
         [0153]     The following description will explain a manner how a mobile station acquires synchronization with a base station when it is turned on with reference to the case illustrated in  FIG. 2  where a time slot to transmit a forward link common control channel signal including a synchronization control channel signal is provided once every four time slots with three other time slots inserted.  
         [0154]     When mobile station  600  is turned on, it does not know an assignment and timing of time slots for reverse link and forward link because it does not acquire synchronization with a base station yet.  
         [0155]     Then mobile station  600 , as illustrated in  FIG. 8 , integrates a correlation value of a received signal with a spreading code of forward link synchronization control channel at each sample timing within a four time slots length  701  starting from an arbitrary time t 1  and repeats the integration at four time slots intervals.  
         [0156]     When the number of integration times is increased, since noise component is reduced, it is detected that an integration value of correlation value at sampling timing  702  illustrated in  FIG. 8  that conforms to a timing of the synchronization control channel signal becomes larger than that at other sampling timing.  
         [0157]     However, as the number of integration times is too increased, a sampling timing by mobile station  600  shifts from the target timing because mobile station  600  does not acquire synchronization with the base station yet. Therefore too large number of integration times makes it difficult to detect timing  702  for synchronization control channel signal.  
         [0158]     When common control channel signals including synchronization control channel signals are not provided at certain intervals, it is difficult to reduce the noise component by the integration described above, making it difficult to detect a timing of synchronization control channel signal.  
         [0159]     However, when common control channel signals including synchronization control channel signals are provided at certain intervals even though the numbers of time slots assigned for reverse link and forward link are varied, it is possible to execute integration at the certain intervals, thus facilitating a detection of the timing of synchronization control channel signal.  
         [0160]     In a configuration of mobile station  600  illustrated in  FIG. 7 , such synchronization acquisition by integration is executed in control section  617 , however a synchronization section (not shown) may be provided besides control section  617 .  
         [0161]     As described above, according to the fifth embodiment, a mobile station detects a synchronization control channel signal by integrating correlation values of a received signal with a spreading code at predetermined time slots intervals, thereby making it possible to acquire synchronization with a base station easily with less time even when an assignment of time slots for forward and reverse links is changed corresponding to an information volume in the case where the information volumes of forward and reverse links are asymmetry.  
         [heading-0162]     (Sixth Embodiment)  
         [0163]      FIG. 9  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to the sixth embodiment of the present invention.  
         [0164]      FIG. 9  illustrates an example where one frame  801  is divided into sixteen time slots  0  to  15 . In  FIG. 9, 802  indicates a time slot at which a forward link common control channel signal is provided,  803  indicates a time slot at which a forward link user information channel signal is provided, and  804  indicates a time slot at which a reverse link user information channel signal is provided.  
         [0165]     In other words, one frame  801  is divided into sixteen time slots so as to provide forward link common control channel signals including synchronization control signals at the eight time slots  0 ,  2 ,  4 ,  6 ,  8 ,  10 ,  12  and  14 , forward link user information channel signals at the time slots  1 ,  5 ,  9  and  13 , and reverse link user information channel signals at the time slots  3  and  11 .  
         [0166]     The transmission power control operation of control section  617  in mobile station  600  illustrated in  FIG. 7  is explained with reference to  FIG. 9 .  
         [0167]     Since the forward link user information channel is an dedicated channel between a mobile station  600  and a base station, the transmission power is controlled so that reception quality at mobile station  600  meets a predetermined requirement.  
         [0168]     On the other hand, since forward link common control channel is a common channel, the transmission power control is not performed based on a requirement of reception quality at mobile station  600 . As a result, the reception quality sometimes deteriorates temporarily due to fading.  
         [0169]     In the case of performing a transmission power control for reverse link under open-loop control, the similarity of propagation paths of reverse link and forward link is used. In this case, when a time interval between a forward link time slot to measure a reception quality and a revere link time slot to transmit, the similarity of propagation path conditions of reverse link and forward link becomes low, resulting in a reduction of accuracy of the transmission power control.  
         [0170]     The high reception quality introduces a more accurate estimation of propagation path conditions, however the propagation path condition changes as an interval between reception and transmission is increased.  
         [0171]     Taking the above problems into consideration, a propagation path condition is estimated by combining a reception quality at each time slot with an appropriate weight. In the case where the propagation path condition changes rapidly, a weight for a common control channel signal at the time slot  2  just before the time slot  3  to be transmitted is set high and weights for a common control channel signal or user information channel signal at the other time slots are set low. It may be performed that the weight for the common control channel signal at the time slot  2  is set at 1 and the weights for a common control channel signal or user information channel signal at the other time slots are set at 0.  
         [0172]     On the other hand, in the case where the propagation path condition changes slowly, since it is possible to estimate the propagation path condition with a high accuracy, a weight for a user information channel signal at the time slot  1  is set high and weights for common control channel signals at the time slots  0  and  2  are set low. It may be performed that the weight for the user information channel signal at the time slot  1  is set at 1 and weights for common control channel signals at time slots  0  and  2  are set at 0.  
         [0173]     In addition, the above case describes about the transmission power control of the reverse link user information channel signal at the time slot  3 , however the same processing is performed to the transmission power control of the reverse link user information channel signal at the time slot  11 .  
         [0174]     The above case further describes about the example where three time slots just before the time slot to be transmitted are used to combine with weights, however it is also preferable to use forward link channel signals at time slots before the three time slots.  
         [0175]     In this case, the above example corresponds to the case where weights for channel signals at time slots four time slots before the time slot to be transmitted are set at 0. In addition, the above case describes that forward user information channel signals are provided at forward link time slots except for forward link time slots at which common control channel signals are provided, however the same processing is performed in another case where forward link user information channel signals and forward link common control channel signals are provided at the same time slots.  
         [0176]     Further, user information channel signals may be provided only at forward link time slots without being provided at reverse link time slots. This case corresponds to weights for user information channel signals being set at 0.  
         [0177]     In addition, a propagation path condition is estimated by combining signals with weights in the above case, however it is also preferable to predict a propagation path condition via which a time slot will be transmitted using a time transition of the estimated propagation path condition to control transmission power.  
         [0178]     Further, in the above case, the transmission power control is performed only under the open-loop control. However, the same processing is performed in the transmission power control under the combination of closed-loop control where a base station instructs transmission power to a mobile station via a forward link.  
         [0179]     As described above, according to the sixth embodiment, a mobile station detects a synchronization control channel signal by integrating correlation values of a received signal with a spreading code at predetermined time slots intervals, thereby making it possible to acquire synchronization with a base station easily with less time even when an assignment of time slots for forward and reverse links is changed corresponding to an information volume in the case where the information volumes of forward and reverse links are asymmetry.  
         [0180]     Further, the mobile station measures a reception quality of a forward link common control channel signal provided at a time slot just before a time slot of a reverse link user information channel signal even though the reverse link user information channel signal is provided at any reverse link time slot, thereby enabling an effective open-loop controlled transmission power control even when a propagation path condition changes rapidly.  
         [heading-0181]     (Seventh Embodiment)  
         [0182]      FIG. 10  is a frame diagram illustrating an assignment of time slots at a communication frame applied in a CDMA/TDD mobile communication system according to the seventh embodiment of the present invention.  
         [0183]      FIG. 10  illustrates an example where one frame  901  is divided into sixteen time slots  0  to  15 . In  FIG. 10, 902  indicates a time slot at which a forward link common control channel signal is provided,  903  indicates a time slot at which a forward link user information channel signal is provided, and  904  indicates a time slot at which a reverse link user information channel signal is provided.  
         [0184]     In other words, one frame  901  is divided into sixteen time slots so as to provide forward link common control channel signals including synchronization control signals at the eight time slots  0 ,  2 ,  4 ,  6 ,  8 ,  10 ,  12  and  14 , forward link user information channel signals at the time slots  5  and  10 , and reverse link user information channel signals at the time slots  3  and  11 .  
         [0185]     The transmission power control operation of control section  617  in mobile station  600  illustrated in  FIG. 7  is explained with reference to  FIG. 10 . In addition, the explanation will describe the case where a weight for forward link channel signal provided at a time slot just before a time slot to be transmitted is 1 and weights for the other forward link channel signals are 0.  
         [0186]     A common control channel signal is provided at the time slot  2  just before the time slot  3  to be transmitted. Accordingly, the transmission power control is performed based on a reception quality of the forward link common control channel signal at the time slot  2 .  
         [0187]     On the other hand, both common control channel signal and user information channel signal are provided at the time slot  10  just before the time slot  11  to be transmitted. Accordingly, it is possible to perform the transmission power control based on both reception qualities of the forward link common control channel signal and user information channel signal.  
         [0188]     Two correction detection sections are necessary to measure both reception qualities of the forward link common control channel signal and user information channel signal. However, a single correlation detection section is enough by providing a configuration where both reception qualities can be switched to measure.  
         [0189]     In a configuration where a reception quality of the forward link common control channel signal is measured, the transmission power control is performed based on the reception quality of the forward link common control channel signal that has a lower accuracy, not depending on the time slot assignment of user information channel signal for forward and reverse links, even when a forward link user information channel signal is provided at a slot just before a slot at which a reverse link user information channel signal is provided.  
         [0190]     Therefore, an effect of transmission power control is decreased. However, by providing a configuration where a channel to measure a reception quality is switched to a user information channel when a forward link user information channel signal is provided at a slot just before a slot at which a reverse link user information channel signal is provided, it is possible to measure the reception quality of the user information channel signal measurable with a high accuracy, thereby enabling an effective transmission power control of the reverse link user information channel signal.  
         [0191]     As described above, according to the seventh embodiment, a mobile station detects a synchronization control channel signal by integrating correlation values of a received signal with a spreading code at predetermined time slots intervals, thereby making it possible to acquire synchronization with a base station easily with less time even when an assignment of time slots for forward and reverse links is changed corresponding to an information volume in the case where the information volumes of forward and reverse links are asymmetry.  
         [0192]     Further, the mobile station switches a reception quality of a forward link common control channel signal and that of a forward link user information signal provided at a time slot just before a time slot of a reverse link user information channel signal even though the reverse link user information channel signal is provided at any reverse link time slot, thereby enabling an effective open-loop controlled transmission power control even when a propagation path condition changes rapidly.  
         [0193]     As been obvious from the above-mentioned explanation, according to the present invention, it is possible for a mobile station to reduce a acquisition time of synchronization with a base station even when an assignment of time slots for forward and reverse links is changed corresponding to an information volume in the case where the information volumes of forward and reverse links are asymmetry, thereby enabling the open-loop controlled transmission power control to function effectively.  
         [0194]     This application is based on the Japanese Patent Application No. HEI10-78317 filed on Mar. 10, 1998, entire content of which is expressly incorporated by reference herein.