Patent Publication Number: US-2007115874-A1

Title: Communication control apparatus and communication control method

Description:
CROSS REFERENCE TO RELATED APPLICATION  
      This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. P2005-310402, filed on Oct. 25, 2005; the entire contents of which are incorporated herein by reference.  
     BACKGROUND OF THE INVENTION  
      1. Field of the Invention  
      The present invention relates to a communication control apparatus and a communication control method, which control communications based on an average value of measured values.  
      2. Description of the Related Art  
      Conventionally, a communication control apparatus is configured to control communications based on an average value of predetermined measured values.  
      As a method of calculating an average value of measured values in such a communication control apparatus, “moving average process” and “weighted average process” are known.  
      The “moving average process” is a process for calculating an average value of measured values, by sliding an interval for calculating an average value.  
      Specifically, such a communication control apparatus is configured to calculate an average value  S n    at timing n, by use of a moving average process, by using measured values S n , S n−1 , S n−2 , S n−3 , . . . and S n−N+1  between the timing n and timing n−N+1 which precedes the timing n by certain intervals (by intervals corresponding to N measured values), in accordance with the following equation.  
           S   n     _     =       ∑     i   =       n   ⁢           ⁢   N     +   1       n     ⁢     S   n           
 
      For example, when the number N of measured values equals five regarding measured values S 1 , S 2 , S 3 , . . . , such a communication control apparatus calculates an average value by use of a moving average process using the measured values S 1  to S 5  at timing  5  when S 5  is measured.  
      In this case, the apparatus calculates an average value by use of the moving average process using the measured values S 2  to S 6  at timing  6  when S 6  is measured.  
      In this case, the apparatus calculates an average value by use of the moving average process using the measured values S 3  to S 7  at timing  7  when S 7  is measured.  
      In such a moving average process, in a case where an average value  S n    of measured values S n  is calculated, N measured values need to be recorded. This causes a problem that a capacity of a recording device has to be large.  
      On the other hand, a weighted average process is a process for calculating an average value of measured values by use of a forgetting factor.  
      Specifically, by used of a weighted average process using a forgetting factor δ, such a communication control apparatus weights an average value  S n−1    at timing n−1 and measured values S n  at timing n, and calculates an average value  S n    at timing n, in accordance with the following equation.
 
   S n   =δ   n   ·  S n 1   +( 1−δ n ) S   n 
 
      It is to be noted that, in general, in such a communication S control apparatus, a forgetting factor δ (0≦δ≦1) is set at a large value (a value slightly smaller than 1) to raise an effect of an average value  S n−1    at timing n−1 on an average value  S n    at timing n.  
      In a weighted average process, in a case where such a communication control apparatus calculates an average value  S n    of measured values S n , it suffices to record an average value  S n−1   , and there is no need to record N measured values unlike a moving average process. This makes it possible to reduce the capacity of the recording device.  
      However, in such a communication control apparatus, in a case where an average value  S 1    at a first timing n (n=1) is calculated by used of a weighted average process using the above-described forgetting factor δ, an initial value needs to be assigned to an average value  S 0    at timing n−1 (n−1=0). Nevertheless, there is a case where an inappropriate initial value is assigned to such an average value  S 0   .  
      In such a case, when the forgetting factor δ (0&gt;δ≦1) is set at a large value (a value slightly smaller than 1), an effect of the inappropriate value assigned to the average value  S 0    becomes high. Therefore, the possibility that an error is caused in an average value  S 1    becomes high.  
      Furthermore, there is also a case where an error of an average value  S 1    causes an error of an average value  S n   .  
      In particular, in a case where enough time has not passed since the first timing n (n=1), the effect of the inappropriate initial value assigned to an average value  S 0    becomes high. Therefore, there is a case where an average value  S n    calculated by used of a weighted average process using a forgetting factor δ assumes a value largely different from an average value calculated by the above-described moving value process.  
      In such a case, the communication control apparatus has a problem that a communication control cannot be appropriately performed based on an average value  S n    calculated by used of a weighted average process using a forgetting factor δ.  
     BRIEF SUMMARY OF THE INVENTION  
      The present invention has been made in view of the forgoing. Accordingly, it is an object of the present invention to provide a communication control apparatus and a communication control method, which makes it possible to control communications with high accuracy based on an average value by reducing errors of the average value due to an inappropriate initial value by causing a forgetting factor to be gradually larger at the time of calculating the average value of measured values by used of a weighted average process using the forgetting factor.  
      A first aspect of the present invention is summarized as a communication control apparatus including a weighted average processor configured to update an average value of measured values at predetermined timings by use of a weighted average process using a forgetting factor; a forgetting factor calculator configured to increase the forgetting factor gradually; and a communication controller configured to control communications based on the average value.  
      In the first aspect, the weighted average processor can be configured to update the average value  S n    at timing n, in accordance with an equation  S n   =δ n ·  S n 1   +(1−δ n )S n , by use of the forgetting factor δ n  at timing n and the average value  S n−1    at timing n−1.  
      In the first aspect, the forgetting factor calculator can be configured to increase the forgetting factor δ n  gradually at timing n, in accordance with an equation  
           δ   n     =     min   ⁡     (       1   -     1   n       ,   δ     )         ,       
 
 up to a predetermined limit value δ. 
 
      In the first aspect, the communication control apparatus can be a radio base station configured to control transmission of downlink user data to mobile stations; the measured values cam be transmission states of the downlink user data to the mobile stations; the weighted average processor can be configured to update an average value of the transmission states at predetermined timings, by use of the weighted average process using the forgetting factor; and the communication controller can be configured to control the transmission of the downlink user data to the mobile stations, based on the average value of the transmission states.  
      In the first aspect, the communication control apparatus can be a radio base station configured to control call admission for mobile stations; the measured values can be maximum allowable transmission rates of uplink user data from the mobile stations; the weighted average processor can be configured to update an average value of the maximum allowable transmission rates at predetermined timings, by use of the weighted average process using the forgetting factor; and the communication controller is configured to control call admission for the mobile stations, based on the average value of the maximum allowable transmission rates.  
      In the first aspect, the communication control apparatus can be a mobile station configured to control a transmission power of a downlink channel from a radio base station; the measured values can be reception signal powers and reception noise interference powers of the downlink channel in the mobile station; the weighted average processor can be configured to update an average value of the reception signal powers and an average value of the reception noise interference powers at predetermined timings by use of the weighted average using the forgetting factor; and the communication controller can be configured to control the transmission power of the downlink channel from the radio base station, based on a ratio between the average value of the reception signal powers and the average value of the reception noise interference powers.  
      A second aspect of the present invention is summarized as a communication control method including; updating, at a communication control apparatus, an average value of measured values at predetermined timings by use of a weighted average process using a forgetting factor; increasing, at the communication control apparatus, the forgetting factor gradually; and controlling, at the communication control apparatus, communications based on the average value.  
      In the second aspect, the average value  S n    at timing n can be updated in accordance with an equation  S n   =δ n ·  S n 1   +(1−δ n )S n , by use of the forgetting factor δ n  at timing n and the average value  S n−1    at timing n−1.  
      In the second aspect, the forgetting factor δ n  at timing n can be gradually increased in accordance with an equation  
           δ   n     =     min   ⁡     (       1   -     1   n       ,   δ     )         ,       
 
 up to a predetermined limit value δ.
 
    
    
     BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS  
       FIG. 1  is a diagram showing a configurational example of a mobile communication system in which a communication control apparatus according to a first embodiment of the present invention is provided.  
       FIG. 2  is a schematic configurational example of the communication control apparatus (a radio base station) according to the first embodiment of the present invention.  
       FIG. 3  is a functional block diagram of a baseband signal process unit of the communication control apparatus (the radio base station) according to the first embodiment of the present invention.  
       FIG. 4  is a functional block diagram of an MAC-hs function unit in the baseband signal process unit of the communication control apparatus (the radio base station) according to the first embodiment of the present invention.  
       FIG. 5  is a flow chart showing an operational example of transmission control process of downlink user data of the communication control apparatus (the radio base station) according to the first embodiment of the present invention.  
       FIG. 6  is a functional block diagram of an MAC-e function unit in a baseband signal process unit of a communication control apparatus (a radio base station) according to a second embodiment of the present invention.  
       FIG. 7  is a flow chart showing an operational example of call admission process to a mobile station of the communication control apparatus (the radio base station) according to the second embodiment of the present invention.  
       FIG. 8  is a schematic configurational example of a communication control apparatus (a mobile station) according to a third embodiment of the present invention.  
       FIG. 9  is a functional block diagram of a baseband signal process unit of the communication control apparatus (the mobile station) according to the third embodiment of the present invention.  
       FIG. 10  is a functional block diagram of a layer  1  function unit in the baseband signal process unit of the communication control apparatus (the mobile station) according to the third embodiment of the present invention.  
       FIG. 11  is a flow chart showing an operational example of transmission control process of a downlink channel of the communication control apparatus (the mobile station) according to the third embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
     Communication Control Apparatus According to First Embodiment of Present Invention  
     Configuration of Communication Control Apparatus According to First Embodiment of Present Invention  
      A configuration of a communication control apparatus according to a first embodiment of the present invention will be described below by referring to FIGS.  1  to  4 .  
       FIG. 1  is a diagram showing a configurational example of a mobile communication system in which a communication control apparatus according to a first embodiment of the present invention is provided.  
      As shown in  FIG. 1 , the mobile communication system according to the first embodiment includes a radio base station  100 , a mobile station  200 , and a radio network controller  300 .  
      Here, the radio network controller  300  may be connected with the radio base station  100  and a plurality of other radio base stations.  
      It is to be noted that the mobile station  200  may be plural, and in the first embodiment, as shown in  FIG. 1 , it is assumed that mobile stations # 1  to #N are in communication with the mobile base station  100 .  
      The mobile communication system according to the first embodiment is adaptable to “W-CDMA” and “CDMA2000” that are the third generation mobile communication systems. In addition, the mobile communication system according to the present embodiment employs HSDPA (High Speed Download Packet Access).  
      Here, the HSDPA is a high-speed transmission method for packets, which uses a downlink shared channel (HS-SCCH (High Speed Shared Control Channel) or HS-DSCH (High Speed Download Shared Channel)), the downlink shared channel being used and shared by the mobile stations # 1  to #N, and which uses associated dedicated channels (uplink and downlink bidirectional channels) that are respectively associated with physical channels individually allocated to the mobile stations # 1  to #N.  
      In the mobile communication system according to the first embodiment, downlink user data are synonymous with downlink packets, and are configured to be transmitted at high speed through the downlink shared channel.  
      In the first embodiment of the present invention, an example will be described in which the above-described communication control apparatus is provided to the mobile base station  100 .  
       FIG. 2  is a schematic configurational example of the radio base station  100  according to the first embodiment.  
      It is to be noted that the following configurations of the radio base station  100  are not necessarily independently present as hardware. That is, the individual configurations may be integrated, or may be configured by processes of software.  
      As shown in  FIG. 2 , the radio base station  100  is provided with an HWY interface  101 , a baseband signal process unit  102 , a transmission and reception unit  103 , an amplifier unit  104 , a transmission and reception antenna  105 , and a call process control unit  106 .  
      The HWY interface  101  is configured to receive downlink user data to be transmitted, from the radio network controller  300  that is positioned uplink of the radio base station  100 , and to input the data to the baseband signal process unit  102 .  
      In addition, the HWY interface  101  is configured to transmit uplink user data from the baseband signal process unit  102  to the radio network controller  300 .  
      The baseband signal process unit  102  is configured to perform a retransmission control (HARQ: Hybrid ARQ) process, a scheduling process, a transmission format selection process, a channel encoding process, a spreading process and the like on the downlink user data, so that the baseband signals including such downlink user data are transmitted to the transmission and reception unit  103 .  
      In addition, the baseband signal process unit  102  is configured to perform a de-spreading process, a RAKE synthetic process, an error correction decoding process and the like on the baseband signals from the baseband signal process unit  102 , and then to transmit the thus obtained uplink user data to the HWY interface  101 .  
      The transmission and reception unit  103  is configured to convert the baseband signals from the baseband signal process unit  102  to radio frequency band signals.  
      In addition, the transmission and reception unit  103  is configured to convert radio frequency band signals from the amplifier unit  104  to baseband signals.  
      The amplifier unit  104  is configured to amplify the radio frequency band signals from the transmission and reception unit  103 , and to transmit the signals by use of the transmission and reception antenna  105 .  
      In addition, the amplifier unit  104  is configured to amplify the signals received by the transmission and reception antenna  105 , and to transmit the signals to the transmission and reception unit  103 .  
      The call process control unit  106  is configured to perform transmission and reception of call process control signals with the radio network controller  300 , and to perform processes such as management of a state of each function unit of the radio base station  100  and hardware resource allocation by a layer  3 .  
       FIG. 3  is a functional block diagram of the baseband signal process unit  102 . As shown in  FIG. 3 , the baseband signal process unit  102  is provided with a layer  1  function unit  111 , an MAC-hs (Medium Access Control-HSDPA) function unit  112 , and an MAC-e function unit  113 ,  
      It is to be noted that each of the layer  1  function unit  111  and the MAC-hs function unit  112  is connected with the call process control unit  106 .  
      The layer  1  function unit  111  is configured to perform a channel encoding process, a spreading process and the like on the downlink user data and control information.  
      In addition, the layer  1  function unit  111  is configured to perform a de-spreading process, a RAKE synthetic process, an error correction decoding process and the like on the uplink user data and the control information.  
      In addition, the layer  1  function unit  111  is configured to receive a downlink SIR (Signal to Interference Ratio), a BLER (Block Error Rate), a CQI (Channel Quality Indicator) and the like transmitted from the mobile stations # 1  to #N by an uplink dedicated DPCCH (Dedicated Physical Control Channel), and to output them to a weighted average process unit  160  of the MAC-hs function unit  112 .  
      In addition, the layer  1  function unit  111  may be configured to output a transmission state of the downlink user data such as a transmission rate of the downlink user data transmitted to the mobile stations # 1  to #N, a size (data volume) of the downlink user data whose delivery confirmation is received from the mobile stations # 1  to #N, a size of the downlink user data transmitted to the mobile stations # 1  to #N, and a size of transmittable downlink user data, to the weighted average process unit  160 . The size of transmittable downlink user data is estimated based on the downlink SIR, BLER, CQI and the like.  
      The MAC-hs function unit  112  is configured to control transmission of the downlink user data, based on the HSDPA.  
      Specifically, the MAC-hs function unit  112  is configured to perform a retransmission control (HARQ) process on the downlink shared channel in the HSDPA, a scheduling process, a transport format process, a resource selection process and the like on the downlink user data waiting for transmission.  
      The MAC-e function unit  113  is configured to control uplink radio resources in an MAC sub-layer.  
       FIG. 4  is a functional block diagram of the MAC-hs function unit  112 .  
      As shown in  FIG. 4 , the MAC-hs function unit  112  is provided with a flow control unit  120 , an MAC-hs resource calculation unit  130 , a scheduler unit  140 , a TFR (Transport Format and Resource) selection unit  150 , and a weighted average process unit  160 .  
      The flow control unit  120  is configured of a plurality of flow controls (# 1  to #N)  121   1 , to  121   N , and is configured to adjust a transmission rate of the downlink user data received from the radio network controller  300  through the HWY interface  101 , based on a capacity of a mounted transmission queue (buffer) and the like.  
      Each of the flow controls (# 1  to #N)  121   1 , to  121   N  is configured to monitor a distribution volume (flow) of the downlink user data.  
      When the distribution volume of the downlink user data increases, and free space of the transmission queue (buffer) decreases, a process is performed to suppress the volume of the downlink user data to be transmitted.  
      It is to be noted that the flow controls (# 1  to #N)  121   1  to  121   N  respectively correspond to connections # 1  to #N with the mobile stations # 1  to #N.  
      The MAC-hs resource calculation unit  130  is to calculate radio resources (a power resource, a code resource, a hardware resource and the like) to be allocated to HS-DSCH.  
      The MAC-hs resource calculation unit  130  is provided with an HS-DSCH power resource calculation unit  131  configured to calculate the power resource, an HS-DSCH code resource calculation unit  132  configured to calculate the code resource, and a hardware resource calculation unit  133  configured to calculate the hardware resource.  
      The scheduler unit  140  is configured to perform a scheduling process on the downlink user data (control of a transmission order of the downlink user data) to be transmitted to the mobile stations # 1  to #N.  
      Specifically, as will be described below, the scheduler unit  140  is configured to select a mobile station #N having a maximum value C max  out of values C N  of evaluation functions with regard to the mobile stations # 1  to #N, and to allocates a priority queue  141  to the mobile station #N (to perform allocation of downlink shared channels). The value C N  of the evaluation functions are calculated in the weighted average process unit  160 .  
      As shown in  FIG. 4 , the scheduler unit  140  is provided with N priority queues (# 1  to #N)  141   1  to  141 N, N reordering units (# 1  to #N)  142   1  to  142   N , and N HARQ units (# 1  to #N)  143   1  and  143   N .  
      It is to be noted that the priority queues (# 1  to #N)  141   1  to  141   N , the reordering units (# 1  to #N)  142   1  to  142   N , and the HARQ units (# 1  to #N)  143   1  to  143   N  respectively correspond to the connections # 1  to #N with the mobile stations # 1  to #N.  
      The priority queues (# 1  to #N)  141   1  to  141   N  are transmission queues provided in every connection. That is, the priority queues (# 1  to #N)  141   1  to  141   N  are configured to store the downlink user data until getting selected by the scheduling process,  
      In general, one priority queue is used for one mobile station. However, in a case where a plurality of connections are set in one mobile station, a plurality of queues are used for one mobile station.  
      The reordering units (# 1  to #N)  142   1  to  142   N  are configured to add sequence numbers to the downlink user data in order that the mobile stations # 1  to #N can perform a reception order control process on the downlink user data in the retransmission control process using the HARQ, and to perform a window control process in order that the reception buffers of the mobile stations # 1  to #N may not overflow.  
      The HARQ units (# 1  to #N)  143   1  to  143   N  are configured to perform a retransmission control process on the downlink user data, based on an Ack/Nack feedback for the downlink user data in accordance with a stop-and-wait protocol ARQ.  
      A TFR selection unit  150  is configured of N TFR selection functions (# 1  to #N)  151   1  to  151   N . It is to be noted that the TFR selection functions (# 1  to #N)  151   1  to  151   N  respectively correspond to the connections # 1  to #N with the mobile stations # 1  to #N.  
      Each of the TFR selection functions (# 1  to #N)  151   1  to  151   N  is configured to determine a downlink transport format (a code modulation method, a modulation multi-valued number, a coding ratio and the like) and a radio resource used in each of the connections # 1  to #N, based on the CQI outputted from the layer  1  function unit  111 , the radio resource (the power resource, the code resource and the hardware resource) and the like that should be allocated to HS-DSCH calculated in the MAC-hs resource calculation unit  130 .  
      Each of the TFR selection functions (# 1  to #N)  151   1  to  151   N  is configured to notify the layer  1  function unit  111  of the determined downlink transport format and radio resource.  
      As will be described below, the weighted average process unit  160  is configured to update, at predetermined timings, an average value of the transmission states of the downlink user data to the mobile stations # 1  to #N, by use of a weighted average process using a forgetting factor.  
      In addition, as will be described below, the weighted average process unit  160  is configured to calculate a value C N  of an evaluation function to be used in the scheduling process by the scheduler unit  140 , based on the average value of the transmission states of the downlink user data to the mobile stations # 1  to #N.  
      In addition, as will be described below, the weighted average process unit  160  is configured to increase a forgetting factor gradually.  
      The weighted average process unit  160  may be configured to increase the forgetting factor gradually at predetermined timings up to a predetermined limit value.  
      It is to be noted that the predetermined timings are, for example, timings for every TTI (Transmission Time Interval), timings for every TTI during which a value C N  of an evaluation function used in the scheduling process is calculated, and for the like.  
     operation of Communication Control Apparatus According to First Embodiment of Present Invention  
      By referring to  FIG. 5 , operations of the communication control apparatus according to the first embodiment of the present invention, specifically, operations of scheduling process of the downlink user data in the MAC-hs function unit  112  will be described.  
      As shown in  FIG. 5 , in Step S 101 , the weighted average process unit  160  performs an initial value assigning process for calculating values C N  of evaluation functions with regard to the mobile stations # 1  to #N.  
      Specifically, the weighted average process unit  160  assigns “N=1”, “C max =0”, and “N max =0” as initial values. Here, “N” represents a subscript of a mobile station, “C max ” represents a maximum value of values C N  of evaluation functions, and “N max ” represents a subscript of a mobile station whose value C N  of the evaluation function becomes the largest.  
      In Step S 102 , the weighted average process unit  160  obtains a transmission state S n  of the downlink user data to the mobile station #N at timing n (that is, an instant transmission state of the downlink user data to the mobile station #N) from the layer  1  function unit  111 .  
      Here, the transmission state S n  of the downlink user data to the mobile station #N at timing n is a transmission rate of the downlink user data transmitted to the mobile station #N, a size (data volume) of the downlink user data whose delivery confirmation is received from the mobile station #N, a size of the downlink user data transmitted to the mobile station #N, a size of transmittable downlink user data, or the like, and is obtained from the layer  1  function unit  111 . The size transmittable downlink user data is estimated based on the downlink SIR, BLER, CQI and the like.  
      In Step S 103 , the weighted average process unit  160  calculates a forgetting factor δ n  at timing n, in accordance with the following equation to increase the forgetting factor δ gradually, based on a convergent forgetting factor δ (a predetermined limit value).  
         δ   n     =     min   ⁡     (       1   -     1   n       ,   δ     )           
 
      In Step S 104 , the weighted average process unit  160  updates an average value  S n    of the transmission state of the downlink user data to the mobile station #N at timing n, in accordance with the following equation, by use of the transmission state S n  obtained in Step S 102  and the forgetting factor δ n  calculated in Step S 103 .
 
   S n   =δ   n   ·  S n 1   +( 1−δ n ) S   n 
 
      Here,  S n−1    is an average value of the transmission state of the downlink user data to the mobile station #N at timing n−1.  
      In Step S 105 , the weighted average process unit  160  calculates a value C N  of an evaluation function to the mobile station #N, in accordance with the following equation by use of the transmission state S n  obtained in Step S 102  and the average value  S n    updated in Step S 104 ,  
         C   N     =       S   n         S   n     _           
 
      In Step S 106 , the weighted average process unit  160  determines whether or not the value C N  of the evaluation function calculated in Step S 105  is larger than the maximum value C max  of the evaluation function.  
      In a case where the value C N  of the evaluation function is lager than the maximum value C max  of the evaluation function (in the case of “YES” in Step S 106 ), since C max =0 (initial value) is currently assigned, the weighted average process unit  160  sets C N  calculated in Step S 105  at C max , and sets the subscription N of the mobile station #N corresponding to C max  to N max  in Step S 107 .  
      In Step S 108 , the weighted average process unit  160  increments a value of N by +1, in order to calculate a value C N+1  of an evaluation function of the next mobile station #N+1.  
      In Step S 109 , the weighted average process unit  160  determines whether or not the value of N is larger than the number of the mobile stations which are in communication with the radio base station  100 .  
      In a case where the value of N is smaller than the number of the mobile stations which are in communication with the radio base station  100  (in the case of “No” in Step S 109 ), in this operation, a loop process from Step S 102  to Step S 108  is repeatedly performed until the value of N exceeds the number of the mobile stations which are in communication with the radio base station  100 .  
      As a result of this, the weighted average process unit  160  can calculate values of evaluation functions with regard to all the mobile stations # 1  to #N which are in communication with the radio base station  100 .  
      On the other hand, in a case where the value of N is larger than the number of the mobile stations which are in communication with the radio base station  100  (in the case of “YES” in Step S 109 ), this operation proceeds to Step S 110 .  
      In Step S 110 , the weighted average process unit  160  instructs the scheduler unit  140  to perform allocation of the transmission queue to the mobile station #N max  corresponding to the N max  set in Step S 107 . The scheduler unit  140  performs the allocation of the transmission queue based on the instruction, and performs the scheduling process of the downlink user data.  
     Action and Effect of Communication Control Apparatus According to First Embodiment of Present Invention  
      In the case of the communication control apparatus according to the first embodiment of the present invention, at the time when the weighted average process unit  160  updates an average value of the transmission states of the downlink user data to the mobile stations by used of a weighted average process using a forgetting factor, the forgetting factor is gradually increased to reduce errors of the average value of the transmission state due to an inappropriate initial value. This makes it possible to perform transmission control of the downlink user data with high accuracy based on the average value of the transmission states.  
      In the case of the communication control apparatus according to the first embodiment of the present invention, it is possible to perform the transmission control of the downlink user data to the mobile stations with high accuracy. This makes it possible to effectively utilize downlink radio resources, and to improve downlink radio quality.  
     Communication Control Apparatus According to Second Embodiment of Present Invention  
     Configuration of Communication Control Apparatus According to Second Embodiment of Present Invention  
      With regard to a configuration of a communication control apparatus according to a second embodiment of the present invention, points different from the configuration and operation of the communication control apparatus according to the first embodiment will be mainly described below.  
      In addition, in the second embodiment, as in the case of the first embodiment, an example will be described in which the above-described communication control apparatus is provided to a radio base station  100 .  
      It is to be noted that the following configurations of the radio base station  100  are not necessarily independently present as hardware. That is, the individual configurations maybe integrated, or may be configured by processes of software.  
      In a mobile communication system in which the communication control apparatus according to the second embodiment is provided, employed is EUL (Enhanced Uplink) that is a method for controlling high speed uplink radio resources in a layer  1  and an MAC sub-layer (a layer  2 ) between the radio base station  100  and mobile stations  200 , which have been discussed by the 3rd Generation Partnership Project (3GPP) and the 3rd Generation Partnership Project 2 (3GPP2) which are international standardization organizations of the third generation mobile communication systems.  
      Therefore, as shown in  FIG. 2 , in the radio base station  100  according to the second embodiment, a baseband signal process unit  102  is configured to be provided with an MAC-e function unit  113  in order to control the uplink radio resources in the MAC sub-layer.  
      In addition, the radio base station  100  according to the second embodiment is configured to transmit the uplink user data from the mobile stations # 1  to #N to the MAC-e function unit  113  through an E-DPC (Enhanced Dedicated Physical Channel) and an E-DHC (Enhanced Dedicated Physical Channel) which is mapped from the E-DPCH in a layer  1  function unit  111 .  
      It is noted that the E-DPCH includes an E-DPDCH (Enhanced Dedicated Physical Data Channel) which transmits the uplink user data from the mobile stations # 1  to #N, and an E-DPCCH (Enhanced Dedicated Physical Control Channel) which transmits control information from the mobile stations # 1  to #N.  
       FIG. 6  is a functional block diagram of the MAC-e function unit  113 .  
      As shown in  FIG. 6 , the MAC-e function unit  113  is provided with an HARQ process unit  113   a , a reception process command unit  113   b , a scheduling unit  113   c , a demultiplex unit  113   d , and a call admission control unit  113   e.    
      The HARQ process unit  113   a  is configured to perform an HARQ process regarding the uplink user data by receiving the uplink user data and HARQ information received from the layer  1  function unit  111 .  
      In addition, the HARQ process unit  113   a  is configured to notify the layer  1  function unit  111  of an ACK/NACK indicating a reception process result regarding the uplink user data. In addition, the HARQ process unit  113   a  is configured to notify the scheduling unit  113   c  of the ACK/NACK.  
      The reception process command unit  113   b  is configured to notify the layer  1  function unit  111  of a spreading rate multi-code number and an encoding rate with regard to a transport format of each specified mobile station, based on an E-TFCI (Enhanced Transport Combination Indicator) for every TTI received from the layer  1  function unit  111 .  
      The scheduling unit  113   c  is configured to change a maximum allowable transmission rate of the uplink user data, based on the E-TFCI for every TTI received from the layer  1  function unit  111 , the ACK/NACK received from the HARQ process unit  113   a , and an interference level of an SIR, an INR or the like.  
      For example, the scheduling unit  113   c  may be configured to decrease the maximum allowable transmission rate of the uplink user data at a constant rate, in a case where the interference level increases to exceed a predetermined value.  
      In addition, the scheduling unit  113   c  may be configured to increase the maximum allowable transmission rate of the uplink user data at a constant rate, in a case where the interference level decreases to fall below a predetermined value.  
      Here, the maximum allowable transmission rate of the uplink user data may be common to all of the mobile stations # 1  to #N which are in communication with the radio base station  100 .  
      It is to be noted that the maximum allowable transmission rate of the uplink user data may be a transmission data block size (TBS) for transmitting the uplink user data, a transmission power of the E-DPDCH obtained from the layer  1  function unit  111 , or a transmission power ratio between the E-DPDCH and the E-DPCCH (offset of transmission power) obtained from the layer  1  function unit  111 .  
      It is to be noted that the scheduling unit  113   c  is configured to notify all of the mobile stations # 1  to #N, which are in communication with the radio base station  100 , of the maximum allowable transmission rate of the uplink user data as scheduling information through the layer  1  function unit  111 .  
      In addition, the scheduling unit  113   c  may be configured to make notification of increase/decrease (UP/DOWN) of the maximum allowable transmission rate of the uplink user data as the scheduling information.  
      The demultiplex unit  113   d  is configured to perform a demultiplex process on the uplink user data received from the HARQ process unit  113   a , and thereby transmitting the thus obtained uplink user data to the HWY interface  101 .  
      The call admission control unit  113   e  is configured to update an average value of the maximum allowable transmission rates of the uplink user data at predetermined timings by use of a weighted average process using a forgetting factor.  
      The call admission control unit  113   e  is configured to obtain the maximum allowable transmission rate of the uplink user data from the scheduling unit  113   c.    
      In addition, as will be described below, the call admission control unit  113   e  is configured to increase a forgetting factor gradually.  
      The call admission control unit  113   e  may be configured to increase the forgetting factor gradually at predetermined timings up to a predetermined limit value.  
      It is to be noted that the predetermined timings are, for example, timings for every TTI or the like.  
      In addition, as will be described below, in a case where a call admission request is made from a mobile Station #N+1 which is not in communication with the radio base station  100 , the call admission control unit  113   e  is configured to determine an average value of the above-described maximum allowable transmission rates of the uplink user data, and to control call admission for the mobile station #N+1.  
      For example, in a case where an average value of the above-described maximum allowable transmission rates of the user data is larger than a threshold value, the call admission control unit  113   e  may be configured to permit call admission of the mobile station #N+1.  
      In addition, in a case where an average of the above-described maximum allowable transmission rates of the uplink user data is not larger than the threshold value, the call admission control unit  113   e  may be configured to refuse the call admission of the mobile station #N+1.  
     Operation of Communication Control Apparatus According to Second Embodiment of Present Invention  
      By referring to  FIG. 7 , operations of the communication control apparatus according to the second embodiment, specifically, operations of the call admission control unit  113   e  to control call admission of the mobile station #N+1 which is not in communication with the radio base station  100 , will be described.  
      As shown in  FIG. 7 , in Step S 201 , the call admission control unit  113   e  obtains a maximum allowable transmission rate S n  of the uplink user data at timing n (that is, an instant maximum allowable transmission rate of the uplink user data) from the scheduling unit  113   c.    
      In Step S 202 , the call admission control unit  113   e  calculates a forgetting factor δ n  at timing n, in accordance with the following equation to gradually increase the forgetting factor δ, based on a convergent forgetting factor δ (a predetermined limit value).  
         δ   n     =     min   ⁡     (       1   -     1   n       ,   δ     )           
 
      In Step S 203 , the call admission control unit  113   e  updates an average value  S n    of the maximum allowable transmission rates of the uplink user data at timing n, in accordance with the following equation by use of the maximum allowable transmission rate S n  obtained in Step S 201  and the forgetting factor δ n  calculated in Step S 202 
 
   S n   =δ   n   ·  S n 1   +( 1−δ n ) S   n 
 
      Here,  S n−1    is an average value of the maximum allowable transmission rates of the uplink user data at timing n−1.  
      In Step S 204 , in a case where a call admission request is made from the mobile station #N+1, this operation proceeds to Step S 205 .  
      In a case where a call admission request is not made from the mobile station #N+1, this operation returns to Step S 201  to repeat Steps S 201  to S 204  at predetermined timings.  
      In Step S 205 , the call admission control unit  113   e  makes a determination on the average value  S n    of the maximum allowable transmission rates updated in Step S 203 .  
      In a case where the average value  S n    of the maximum allowable transmission rates updated in Step S 203  is larger than a threshold value (in the case of “YES” in Step S 205 ), the call admission control unit  113   e  permits call admission of the mobile station #N+1 in Step S 206 .  
      In a case where the average value  S n    of the maximum allowable transmission rates updated in Step S 203  is not larger than the threshold (in the case of “NO” in Step S 205 ), the call admission control unit  113   e  refuses the call admission of the mobile station #N+1 in Step S 207 .  
     Action and Effect of Communication Control Apparatus According to Second Embodiment  
      According to the communication control apparatus according to the second embodiment of the present invention, at the time when the call admission control unit  113   e  updates an average value of the maximum allowable transmission rates of the uplink user data by used of a weighted average process using a forgetting factor, the forgetting factor is gradually increased to reduce errors of the average value of the maximum allowable transmission rates due to an inappropriate initial value. This makes it possible to control call admission of the mobile stations with high accuracy, based on the average value of the maximum allowable transmission rates.  
      According to the communication control apparatus according to the second embodiment of the present invention, since it is possible to control the call admission of the mobile stations with high accuracy, it is possible to effectively utilize uplink radio resources, and to improve uplink radio quality.  
     Communication Control Apparatus According to Third Embodiment of Present Invention  
     Configuration of Communication Control Apparatus According to Third Embodiment of Present Invention  
      With regard to a configuration of a communication control apparatus according to a third embodiment of the present invention, points different from the configuration and operation of the mobile communication system set in the communication control apparatus according to the above-described first and second embodiments will be mainly described below.  
      In addition, in a mobile communication system according to the third embodiment, transmission power control of downlink channel by use of a closed loop is employed.  
      It is to be noted that in the third embodiment of the present invention, an example in which the above-described communication control apparatus is provided to a mobile station  200  will be described.  
       FIG. 8  is a diagram showing a schematic configurational example of the mobile station  200  according to the third embodiment.  
      It is to be noted that the following configurations of the mobile station  200  are not necessarily independently present as hardware, That is, the individual configurations may be integrated, or may be configured by processes of software.  
      As shown in  FIG. 8 , the mobile station  200  is provided with a bus interface unit  201 , a call process control unit  202 , a baseband signal process unit  203 , a transmission and reception unit  204 , and a transmission and reception antenna  205 . In addition, the mobile station  200  may be configured to be provided with an amplifier unit (not shown).  
      The call process control unit  202  is connected with the bus interface unit  201  and the baseband signal process unit  203 . The call process control unit  202  is configured to perform state management of each function unit, and the like.  
      As shown in  FIG. 9 , the baseband signal process unit  203  is provided with an upper layer function unit  211 , an RLC function unit  212  configured to function as an RLC sub-layer, an MAC-d function unit  213 , an MAC-e function unit  214 , and a layer  1  function unit  215  configured to function as a layer  1 .  
      The transmission and reception unit  204  is configured to convert baseband signals from the baseband signal process unit  203  to radio frequency band signals, In addition, the transmission and reception unit  204  is configured to convert radio frequency band signals from the transmission and reception antenna  205  to baseband signals.  
       FIG. 10  is a functional block diagram of the layer  1  function unit  215  of the baseband signal process unit  203 .  
      As shown in  FIG. 10 , the layer  1  function unit  215  is provided with a physical channel reception unit  215   a , a transmission channel decoder unit  215   b , an SINR measurement unit  215   c , an SINR comparison unit  215   d , a transmission channel encoder unit  215   e , and a physical channel transmission unit  215   f.    
      The physical channel reception unit  215   a  is configured to receive downlink user data and control information from the radio base station  100  through a physical channel such as a CPICH (Common Pilot Channel) or a DPCH (Dedicated Physical Channel), and to perform de-spreading process and the like to output reception signals.  
      Here, a DPCH is an uplink and downlink bidirectional channel, and includes a DPDCH (Dedicated Physical Data Channel) for transmitting user data, and a DPDCH (Dedicated Physical Control Channel) for transmitting control information.  
      The transmission channel decoder unit  215   b  is configured to perform a RAKE synthesis process, an error correction decoding process and the like, based on the reception signals outputted from the physical channel reception unit  215   a , and to transmit the downlink user data to the MAC-e function unit  214 .  
      The SINR measurement unit  215   c  is configured to measure a SINR (signal to interference-plus-noise ratio) based on the reception signals of the downlink channel, the reception signals being outputted from the physical channel reception unit  215   a.    
      specifically, the SINR measurement unit  215   c  is configured to obtain reception signal powers and reception noise interference powers of the CPICH, based on the reception signals of CPICH, the reception signals being outputted from the physical channel reception unit  215   a.    
      In addition, the SINR measurement unit  215   c  is configured to update an average value of the reception signal powers and an average value of the reception noise interference powers of the CPICH at predetermined timings, by use of a weighted average process using a forgetting factor.  
      In addition, the SINR measurement unit  215   c  is configured to measure an SINR that is a ratio between the updated average value of the reception signal powers and the updated average value of the reception noise interference powers of the CPICH.  
      In addition, the SINR measurement unit  215   c  may be configured to measure SINR, based on dedicated pilot signals included in the DPCCH.  
      In addition, as will be described below, the SINR measurement unit  215   c  is configured to increase a forgetting factor gradually.  
      The SINR measurement unit  215   c  may be configured to increase the forgetting factor gradually at predetermined timings up to a predetermined limit value.  
      It is to be noted that the predetermined timings are, for example, timings for every TTI or the like.  
      The SINR comparison unit  215   d  is configured to perform transmission power control of the downlink channel from the radio base station  100 , based on an SINR.  
      Specifically, the SINR comparison unit  215   d  is configured to compare the SINR measured by the SINR measurement unit  215   c  with a target SINR, and to output a transmission power control bit, based on the comparison result.  
      Here, the target SINR is a target value of SINR, which is determined based on an error rate or the like in the error correction decoding process in order to secure reception quality.  
      For example, in a case where the SINR calculated by the SINR measurement unit  215   c  is lower than the target SINR, the SINR comparison unit  215   d  may output a transmission power control bit instructing increase (UP) of the transmission power of the downlink channel.  
      The transmission channel encoder unit  215   e  is configured to perform an error correction encoding process, a transmission rate matching process and the like on the uplink user data and the control information.  
      The physical channel transmission unit  215   f  is configured to perform a spreading process or the like on the uplink user data and the control information, and to transmit them through the physical channel.  
      In addition, the physical channel transmission unit  215   f  is configured to transmit the transmission power control bit by use of the DPCCH to the radio base station  100 .  
     Operation of Communication Control Apparatus According to Third Embodiment of Present Invention  
      By referring to  FIG. 11 , operations of the communication device according to the third embodiment of the present invention, specifically, operations in which the mobile station  200  performs transmission power control of the downlink channel from the radio base station  100  will be described.  
      As shown in  FIG. 11 , in Step S 301 , the SINR measurement unit  215   c  obtains the reception signal outputted from the physical channel reception unit  215   a.    
      In Step S 302 , the SINR measurement unit  215   c  obtains a reception signal power S 1   n  at timing n (that is, an instant reception signal power) based on the reception signal obtained in Step S 301 .  
      In Step S 303 , the SINR measurement unit  215   c  calculates a forgetting factor δ 1   n  at timing n, based on a convergent forgetting factor δ 1  (a predetermined limit value), in accordance with the following equation to increase the forgetting factor δ 1  gradually.  
         δ   ⁢           ⁢     1   n       =     min   ⁡     (       1   -     1   n       ,     δ   ⁢           ⁢   1       )           
 
      In Step S 304 , the SINR measurement unit  215   c  updates the average value  S 1   n    in of the reception signal powers at timing n, in accordance with the following equation by use of the reception signal power S 1   n  obtained in Step S 302  and the forgetting factor δ 1   n  calculated in Step S 303 .
 
   S1 n   =δ 1 n   ·  S1 n−1   +( 1−δ1 n ) S 1 n 
 
      Here,  S 1   n−1    is an average value of the reception signal powers at timing n−1.  
      In Steps S 305  to S 307 , as in the case of Steps S 302  to S 304 , an average value  S 2   n    of the reception noise interference powers at timing n (that is, instant reception noise interference power) is updated.  
      In Step S 308 , the SINR measurement unit  215   c  updates SINR in accordance with the following equation,  
         S   ⁢           ⁢   I   ⁢           ⁢   N   ⁢           ⁢   R     =         S   ⁢           ⁢     1   n       _         S   ⁢           ⁢     2   n       _           
 
      In Step S 309 , the SINR comparison unit  215   d  determines whether or not the SINR updated in Step S 308  is larger than a target SINR.  
      In a case where the SINR is larger than the target SINR (in the case of “YES” in Step S 309 ), the SINR comparison unit  215   d  outputs a transmission power control bit to decrease the transmission power of the downlink channel in Step S 310 .  
      In a case where the SINR is the target SINR and less (in the case of “NO” in Step S 309 ), the SINR comparison unit  215   d  outputs a transmission power control bit to increase the transmission power of the downlink channel in Step S 311 .  
     Action and Effect of Communication Control Apparatus According to Third Embodiment of Present Invention  
      In the case of the communication control apparatus according to the third embodiment of the present invention, at the time when the SINR measurement unit  215   c  updates an average value of the reception signal powers and an average value of the reception noise interference powers by use of a weighted average process using a forgetting factor, the forgetting factor is gradually increased, thereby reducing errors of the average value of the reception signal powers and errors of the average value of the reception noise interference powers, the errors being due to an inappropriate initial value.  
      This makes it possible to control transmission power of the downlink channel from the radio base station with high accuracy, based on a ratio between the average value of the reception signal powers and the average value of the reception noise interference powers.  
      In the case of the communication control apparatus according to the third embodiment of the present invention, since it is possible to control the transmission power of the downlink channel from the radio base station with high accuracy, it is possible to effectively utilize downlink resources, and to improve downlink radio quality.  
     Modified Example  
      The communication control apparatus according to the third embodiment of the present invention may be configured to update an average value of the reception signal powers and an average value of the reception interference powers, and to control the transmission power of the downlink channel based on an SIR that is a ratio between the average value of the reception signal powers and the average value of the reception interference powers.  
     Other Embodiments  
      The present invention has been described by use of the above-described embodiments. However, it should not be understood that the description and drawings constituting a part of this disclosure limit the present invention. Various alternative embodiments, examples and operational technologies will be obvious to those skilled in the art from this disclosure.  
      For example, the communication control apparatus according to the present invention can be installed in a radio network controller.