Abstract:
Random access technology is provided for establishing an individual channel between a radio communication terminal device and a base station device in a short time and a radio communication terminal device executing the random access method. A RACH sub-channel allocation unit allocates a transmission packet input from a replication unit to an arbitrary sub-carrier at the RACH arbitrary time slot at random. An allocation unit judges whether an overlap is generated in the allocation result obtained by the RACH sub-channel allocation unit.

Description:
PRIORITY APPLICATIONS 
       [0001]    This is a continuation application of application Ser. No. 13/158,014, filed Jun. 10, 2011, which is a continuation application of application Ser. No. 12/965,641, filed Dec. 10, 2010, now U.S. Pat. No. 8,000,295, which is a continuation application of application Ser. No. 10/591,712 filed Sep. 6, 2006, now U.S. Pat. No. 7,873,000, which is a national stage of PCT/JP2005/003329 filed Feb. 28, 2005, which is based on Japanese Application No. 2004-065625 filed Mar. 9, 2004, the entire contents of each which are incorporated by reference herein. 
     
    
     TECHNICAL FIELD 
       [0002]    The present invention relates to a random access method in a radio communication system composed of a plurality of radio communication terminal apparatuses and base station apparatuses, and a radio communication terminal apparatus of the random access method. 
       BACKGROUND 
       [0003]    Conventionally, in a radio communication system by a cellular scheme, when a radio communication terminal apparatus starts or restarts communication, an individual channel between the radio communication terminal apparatus and the base station apparatus is not established yet, and the radio communication terminal apparatus is therefore designed to attempt an access to the base station apparatus using a random access channel (hereinafter “RACH”: Random Access Channel). For example, in the radio communication system by a W-CDMA scheme, a slotted ALOHA scheme is adopted. When each of a plurality of radio communication terminal apparatuses start or restart communication, access to the base station apparatus is attempted at an arbitrary timing out of start timing candidates (RACH subchannel). If there is no response from the base station apparatus within predetermined time from the access time, the access is determined failed, and access to the base station apparatus is attempted again (see, for example, Non-Patent Document 1). 
         [0004]    Further, in the radio communication system by a multi-carrier transmission scheme, a technology is known in which when transmission packet is transmitted to the base station apparatus by RACH for establishing an individual channel, the radio communication terminal apparatus selects slot (timing) and subcarrier (frequency) of RACH and spreading code based on certain conditions, spreads the transmission packet by the selected spreading code, and then transmits the packet to the base station apparatus at the selected tuning and frequency (see, for example, Patent Document 1). Furthermore, in a technology disclosed in Patent Document 1, a radio communication terminal apparatus attempts an access to the base station apparatus, and if there is no response from the base station apparatus within predetermined time from the access time, the radio communication terminal apparatus attempts an access to the base station apparatus again.
   Patent Document 1: Japanese Patent Application Laid-Open No. 2001-268051   Non-Patent Document 1: Keiji Tachikawa (ed.), “W-CDMA Mobile Communication Scheme,” Maruzen Co., Ltd., p. 45, Jun. 25, 2001   
 
       DISCLOSURE 
       [0007]    However, in technologies disclosed in Patent Document 1 and Non-Patent Document 1, a plurality of radio communication terminal apparatuses attempt an access to the base station apparatus by RACH and access to the base station apparatus is attempted again after determining success or failure for establishing individual channels so that a case may occur when establishing the individual channel after the first access to the base station apparatus may require time. Furthermore, the number of transmission packets transmitted by RACH increases as the number of radio communication terminal apparatuses belonging to the same cell increases so that the likelihood of collision of transmission packets becomes high and establishing the individual channels requires longer time. For this reason, with the conventional technology, the problems of deterioration of communication quality and non-accessible state for communication and the like are made more likely to occur in the radio communication terminal apparatus designed to plan a service demanding a QoS (Quality of Service) delay requirement. 
         [0008]    It is therefore an object of the present invention to provide a random access method for establishing an individual channel between a radio communication terminal apparatus and a base station apparatus in a short time, and a radio communication terminal apparatus for operating this random access method. 
         [0009]    A Random access method according to the present invention includes a duplication step of duplicating a transmission packet, an assignment step of assigning each of a plurality of duplicated transmission packets to a random access channel, and a transmission step of transmitting the plurality of the transmission packets in accordance with an assignment result in the assignment step. 
         [0010]    According to this method, the radio communication terminal apparatus assigns and transmits a plurality of transmission packets to the base station apparatus by RACH so that, even when many radio communication terminal apparatuses belong to the same cell, the likelihood becomes high that, one of the plurality of transmission packets is received by the base station apparatus without colliding with transmission packets transmitted from other radio communication terminal apparatuses. As a result, according to this method, the radio communication terminal apparatus transmits the duplicated transmission packets to RACH without waiting for a response from the base station apparatus to confirm whether or not the transmission packets transmitted to RACH are received at the base station apparatus, thereby establishing an individual channel to the base station apparatus in a short time. 
         [0011]    The random access method according to the present invention includes, in the above-mentioned invention, a determination step of determining the number of duplications of the transmission packet in the duplication step according to a priority of service planned after communication is started. 
         [0012]    According to this method, in addition to the effect of the invention, the number of transmission packets transmitted to RACH by the radio communication terminal apparatus is determined according to kinds of services planned after the individual channel is established so that, out of the plurality of the radio communication terminal apparatuses belonging to the same cell, one with higher urgency is more likely to establish the individual channel. As a result, according to this method, the problems of deterioration of communication quality, non-accessible state for communication and the like are made less likely to occur in the plurality of the whole radio communication terminal apparatuses belonging to the same cell. 
         [0013]    The random access method according to the present invention includes, in the above-mentioned invention, a determination step of determining the number of duplications of the transmission packet in the duplication step according to the number of retransmissions of the transmission packet. 
         [0014]    According to this method, in addition to the effect of the invention, the number of duplications of the transmission packet increases according to the number of retransmissions of transmission packets so that, out of the plurality of the radio communication terminal apparatuses belonging to the same cell, one with higher urgency is more likely to establish the individual channel. As a result, according to this method, the problems of deterioration of communication quality, non-accessible state for communication and the like are made less likely to occur in the plurality of the whole radio communication terminal apparatuses belonging to the same cell. 
         [0015]    The random access method according to the present invention includes, in the above-mentioned invention, a determination step of determining the number of duplications of the transmission packet in the duplication step according to the number of the radio communication terminal apparatuses belonging to the same cell and using said random access channel. 
         [0016]    According to this method, in addition to the effect of the invention, if the number of the radio communication terminal apparatuses belonging to the same cell increases, radio communication terminal apparatuses make less the number of the duplications of the transmission packet so that it is possible to reduce the likelihood of collision of transmission packets. As a result, according to this method, the problems of deterioration of communication quality, non-accessible state for communication and the like are made less likely to occur in the plurality of the whole radio communication terminal apparatuses belonging to the same cell. 
         [0017]    With the random access method according to the present invention, in the assignment step of the above-mentioned invention, each of the plurality of duplicated transmission packets are assigned to one of time slots in the random access channel. 
         [0018]    With the random access method according to the present invention, in the assignment step of the above-mentioned invention, each of the plurality of duplicated transmission packets are assigned to one of subcarriers in the random access channel. 
         [0019]    According to these methods, in addition to the effect of the invention, the radio communication terminal apparatus assigns the plurality of transmission packets randomly to one of time slots and subcarriers of RACH so that it is possible to reduce load of the signal processing necessary for the assignment of transmission packets in the radio communication terminal apparatus. 
         [0020]    With the random access method according to the present invention, in the assignment step of the above-mentioned invention, each of the plurality of duplicated transmission packets are assigned to one of time slots and one of subcarriers in the random access channel. 
         [0021]    According to this method, in addition to the effect of the invention, the radio communication terminal apparatus assigns the plurality of transmission packets randomly to time slots and subcarriers of RACH so that, even when many radio communication terminal apparatuses belong to the same cell, it is possible to reduce the likelihood of collision of the transmission packets. 
         [0022]    With the random access method according to the present invention, in the assignment step of the above-mentioned invention, each of the plurality of duplicated transmission packets are assigned to one of spreading codes in the random access channel. 
         [0023]    According to this method, in addition to the effect of the invention, the plurality of radio communication terminal apparatuses spread and transmit the transmission packets to the base station apparatus using the spreading codes selected randomly so that, even when many radio communication terminal apparatuses belong to the same cell, it is possible to reduce the likelihood of collision of transmission packets. 
         [0024]    A radio communication terminal apparatus according to the present invention adopts a configuration having: a duplication section that duplicates a transmission packet; an assignment section that assigns each of the plurality of duplicated transmission packets to a random access channel; and a transmission section that transmits the plurality of transmission packets in accordance with an assignment result in the assignment section. 
         [0025]    According to this configuration, the radio communication terminal apparatus assigns the plurality of the duplicated transmission packets randomly to RACH and transmits the transmission packets to the base station apparatus so that, even when many radio communication terminal apparatuses belong to the same cell, the likelihood becomes high that, the plurality of transmission packets are received by the base station apparatus without colliding with transmission packets transmitted from other radio communication terminal apparatuses. As a result, according to this configuration, the radio communication terminal apparatus transmits the duplicated transmission packets to RACH without waiting for a response from the base station to confirm whether or not the transmission packets transmitted to RACH are received at the base station, thereby establishing an individual channel to the base station apparatus in a short time. 
         [0026]    According to the present invention, the plurality of the radio communication terminal apparatuses assign the plurality of the duplicated transmission packets randomly to RACH and transmits the transmission packets to the base station apparatus so that, even when many radio communication terminal apparatuses belong to the same cell, the likelihood becomes high that, the plurality of transmission packets are received by the base station apparatus without colliding with transmission packets transmitted from other radio communication terminal apparatuses. As a result, according to this invention, the radio communication terminal apparatus transmits the duplicated transmission packets to RACH without waiting for a response from the base station apparatus to confirm whether or not the transmission packets transmitted to RACH are received at the base station, thereby establishing an individual channel to the base station in a short time. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0027]      FIG. 1  shows a configuration of a radio communication terminal system using a random access method according to Embodiment 1 of the present invention; 
           [0028]      FIG. 2  is a block diagram showing a configuration of a radio communication terminal apparatus according to Embodiment 1 of the present invention; 
           [0029]      FIG. 3  is a flow chart explaining a random access method according to Embodiment 1 of the present invention; 
           [0030]      FIG. 4A  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0031]      FIG. 4B  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0032]      FIG. 4C  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0033]      FIG. 4D  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0034]      FIG. 5A  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0035]      FIG. 5B  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0036]      FIG. 5C  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0037]      FIG. 5D  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0038]      FIG. 5E  shows an assignment of a transmission packet to RACH according to Embodiment 1; 
           [0039]      FIG. 6  is a block diagram showing a configuration of a radio communication terminal apparatus according to Embodiment 2 of the present invention; 
           [0040]      FIG. 7  is a flow chart explaining a random access method according to Embodiment 2 of the present invention; 
           [0041]      FIG. 8  is a block diagram showing a configuration of a radio communication terminal apparatus according to Embodiment 3 of the present invention; 
           [0042]      FIG. 9  is a flow chart explaining a random access method according to Embodiment 3 of the present invention; 
           [0043]      FIG. 10  is a block diagram showing a configuration of a radio communication terminal apparatus according to Embodiment 4 of the present invention; 
           [0044]      FIG. 11  is a flow chart explaining a random access method according to Embodiment 4 of the present invention; 
           [0045]      FIG. 12A  shows a correlation between a priority, the number of the radio communication terminal apparatuses belonging to the same cell, and the number of duplications of a transmission packet according to Embodiment 4; and 
           [0046]      FIG. 12B  shows a correlation between a priority, the number of the radio communication terminal apparatuses belonging to the same cell, and the number of duplications of a transmission packet according to Embodiment 4. 
       
    
    
     DETAILED DESCRIPTION 
     Example Embodiment 1   
       [0047]      FIG. 1  shows a schematic configuration of a radio communication system composed of four radio communication terminal apparatuses  200 - 1  to  200 - 4  and base station apparatus  100  that establish individual channels using a random access method according to Embodiment 1 of the present invention. In  FIG. 1 , a communication area of this radio communication system is indicated as “cell A.” Furthermore, an OFDM (Orthogonal Frequency Division Multiplexing) signal is subjected to packet exchange in cell A of  FIG. 1 . In addition, the configurations and operations of the radio communication terminal apparatuses  200 - 1  to  200 - 4  will be explained below, but the radio communication terminal apparatuses  200 - 1  to  200 - 4  refer to the same configuration and the same function so that the branch numbers may be omitted when explanations of the function and the like are made entirely. 
         [0048]      FIG. 2  is a block diagram showing a configuration of radio communication terminal apparatus  200 . Radio communication terminal apparatus  200  includes transmission packet generating section  201 , duplication section  202 , assignment section  210 , packet multiplexing section  221 , radio transmission section  222  and antenna element  223 . Furthermore, assignment section  210  includes RACH subchannel assigning sections  211 - 1  to  211 - c.  In addition, “c” is an arbitrary natural number of two or greater. 
         [0049]    Transmission packet generating section  201  generates transmission packet including information of radio communication terminal apparatus  200  necessary for establishing an individual channel to base station apparatus  100  when radio communication terminal apparatus  200  is started or recovered from the idol state, and inputs the generated transmission packet to duplication section  202 . 
         [0050]    Duplication section  202  duplicates the transmission packet input from transmission packet generating section  201 , and inputs c duplicated transmission packets to RACH subchannel assigning sections  211 - 1  to  211 - c,  respectively. 
         [0051]    RACH subchannel assigning section  211  assigns the transmission packets input from duplication section  202  randomly to arbitrary subcarriers with arbitrary RACH time slots. Assignment section  210  compares the assignment results of RACH subchannel assigning sections  211 - 1  to  211 - c  each other, and when transmission packets are assigned to the same subcarrier with the same time slot with overlap, assignment section  210  instructs one of RACH subchannel assigning sections  211  to perform assignment again. Assignment section  210  then instructs RACH subchannel assigning sections  211 - 1  to  211 - c  to input transmission packets to packet multiplexing section  221  with the subcarriers of assigned time slots after confirming that time slots and subcarriers assigned by RACH subchannel assigning sections  211 - 1  to  211 - c  are not overlapped. RACH subchannel assigning sections  211 - 1  to  211 - c  input transmission packets at predetermined timing and frequency to packet multiplexing section  221  in accordance with instructions from assignment section  210 . 
         [0052]    Packet multiplexing section  221  multiplexes transmission packets input from RACH subchannel assigning sections  211 - 1  to  211 - c  and inputs multiplexed transmission packets to radio transmission section  222 . 
         [0053]    Radio transmission section  222  is composed of S/P converter, IFFT apparatus, P/S converter, guard interval insertion apparatus, bandpass filter, D/A converter, low noise amplifier or the like, and after generating an OFDM (Orthogonal Frequency Division Multiplexing) signal from the transmission packet input from packet multiplexing section  221 , radio transmission section  222  transmits the generated OFDM signal by radio to base station apparatus  100  through antenna element  223 . 
         [0054]    Next, the operations of radio communication terminal apparatus  200  will be explained using  FIG. 3 .  FIG. 3  is a flow chart showing steps of a random access method according to this embodiment. 
         [0055]    First, in step ST 310 , duplication section  202  duplicates c transmission packets input from transmission packet generating section  201 . 
         [0056]    Next, in step ST 320 , RACH subchannel assigning sections  211 - 1  to  211 - c  assign the transmission packets input from duplication section  202  randomly to arbitrary subcarriers at arbitrary time slots of RACH. 
         [0057]    Next, in step ST 330 , assignment section  210  determines whether or not assignment results by RACH subchannel assigning sections  211 - 1  to  211 - c  are overlapped. When assignment section  210  determines assignment results by RACH subchannel assigning section  211  are overlapped in step ST 330 , assignment section  210  makes one of RACH subchannel assigning sections  211  which has caused the overlap perform the assignment of step ST 320  again. On the other hand, in step ST 330 , when assignment section  210  determines assignment results by RACH subchannel assigning section  211  are not overlapped, step ST 340  is executed. 
         [0058]    Next, in step ST 340 , radio transmission section  222  generates an OFDM signal from the transmission packet input from packet multiplexing section  221 , and transmits the generated OFDM signal by radio to base station apparatus  100  by RACH through antenna element  223 . 
         [0059]      FIGS. 4A to 4D  and  FIGS. 5A to 5E  show specific aspect of assigning a transmission packet to the arbitrary subcarriers at arbitrary time slots of RACH by the random access method according to this embodiment. In this embodiment, RACH subchannel assigning section  211  is taken to process five subcarriers (SC) and five time slots (TS) as a unit of RACH and assigns transmission packets randomly within this one unit. As can be seen in  FIG. 4A , for example, transmission packets (RACH access signals) are continuously transmitted using five consecutive time slots TS1, TS2, TS3, TS4, TS5 and are consecutive in the time domain. 
         [0060]      FIG. 4A  shows an assignment of transmission packets to RACH in radio communication terminal apparatus  200 - 1 , and  FIG. 4B  to  FIG. 4D  show radio communication terminal apparatuses  200 - 2  to  200 - 4 , respectively.  FIG. 4A  and  FIG. 4D  show an aspect of randomly assigning transmission packets to one of time slots and to one of subcarriers of RACH, and  FIG. 4B  to one of subcarriers by all time slots of RACH, and  FIG. 4C  to one of time slots in SC3 of RACH. 
         [0061]      FIGS. 5A to 5E  show transmission conditions of radio communication terminal apparatuses  200 - 1  to  200 - 4  about SC1 to SC5 in timings of TS1 to TS5, in the case that radio communication terminal apparatuses  200 - 1  to  200 - 4  transmit transmission packets by the assignment aspects shown in  FIGS. 4A to 4D .  FIG. 5A  shows a transmission condition in TS1,  FIG. 5B  in TS2,  FIG. 5C  in TS3,  FIG. 5D  in TS4 and  FIG. 5E  in TS5, respectively.  FIGS. 5A to 5E  append “x” to all colliding transmission packets and “o” to transmission packets first received at base station apparatus  100 , per radio communication terminal apparatuses  200 - 1  to  200 - 4 . 
         [0062]    As shown in  FIGS. 5A to 5E , individual channels can be established to base station apparatus  100 , at a timing of TS1 in radio communication terminal apparatus  200 - 1 , at a timing of TS3 in radio communication terminal apparatus  200 - 2 , at a timing of TS5 in radio communication terminal apparatus  200 - 3  and at a timing of TS4 in radio communication terminal apparatus  200 - 4 , respectively. 
         [0063]    In this way, according to this embodiment, radio communication terminal apparatus  200  assigns a plurality of duplicated transmission packets to RACH randomly in RACH subchannel assigning sections  211 - 1  to  211 - c,  and transmits the transmission packets at the assigned time slots and subcarriers without waiting for a response from base station apparatus  100  to the first transmission packets, thereby establishing an individual channel to base station apparatus  100  in a short time. 
         [0064]    Furthermore, a plurality of transmission packets are assigned to time slots of RACH randomly only according to radio communication terminal apparatus  200 - 2  of this embodiment, and to subcarrier of RACH only according to radio communication terminal apparatus  200 - 3  so that it is possible to reduce load of signal processing in RACH subchannel assigning section  211  necessary for the assignment of transmission packets compared to the case that the plurality of transmission packets are assigned to time slots and subcarriers of RACH randomly. 
         [0065]    Moreover, according to radio communication terminal apparatus  200 - 1  or  200 - 4  of this embodiment, RACH subchannel assigning section  211  assigns a plurality of transmission packets to one of time slots of RACH and also to one of subcarriers of RACH randomly so that, even when many radio communication terminal apparatuses  200  belong to the same cell, it is possible to reduce the likelihood of collision of transmission packets in RACH. 
         [0066]    In addition, the following applications and changes may be possible to the random access method and radio communication terminal apparatus  200  according to this embodiment. 
         [0067]    In this embodiment, a case has been described where a plurality of radio communication terminal apparatuses  200  assign transmission packets randomly to time slots and subcarriers of RACH, but the present invention is not limited to this, and, for example, it is equally possible for a plurality of radio communication terminal apparatuses  200  to transmit not OFDM but packet signals of a single carrier by radio communication, and assign those packet signals randomly to the arbitrary time slots of RACH. 
         [0068]    Furthermore, in this embodiment, a case has been described where radio communication terminal apparatus  200  assigns randomly and transmits transmission packets to time slots and subcarriers of RACH, but the present invention is not limited to this, and, for example, it is possible for radio communication terminal apparatus  200  to select spreading codes randomly instead of time slots and subcarriers of RACH, and also perform code division of the transmission packets using the selected spreading codes. Furthermore, it is possible for radio communication terminal apparatus  200  to assign transmission packets randomly to RACH subchannel where time slots, subcarriers and spreading codes are setting elements. As a result, even when many radio communication terminal apparatuses  200  belong to the same cell, it is possible to further reduce the likelihood of collision of transmission packets in RACH. 
       Example Embodiment 2 
       [0069]      FIG. 6  is a block diagram showing a configuration of radio communication terminal apparatus  600  according to Embodiment 2 of the present invention. Radio communication terminal apparatus  600  further includes priority determining section  601  and number-of-duplications determining section  602  in radio communication terminal apparatus  200  explained in Embodiment 1. Therefore, radio communication terminal apparatus  600  includes many components to show the same function as in the components of radio communication terminal apparatus  200 , so that such components are assigned the same reference numerals as in the components of radio communication terminal apparatus  200 , and explanations thereof will be omitted. 
         [0070]    Priority determining section  601  determines a priority according to kinds of services planned by radio communication terminal apparatus  600  after communication with base station apparatus  100  is started. For example, in call services and video streaming services, since allowable delay time is short (QoS delay requirement is demanding), priority determining section  601  determines that high priority is necessary in radio communication terminal apparatus  600  scheduled to plan such service. Priority determining section  601  then inputs information of the determined priority to number-of-duplications determining section  602 . 
         [0071]    Number-of-duplications determining section  602  compares priority information input from priority determining section  601  with a conversion table provided in advance, determines the number of duplications corresponding to the priority and inputs information of, the determined number of duplications to duplication section  202 . 
         [0072]    Next, the operations of radio communication terminal apparatus  600  will be explained using  FIG. 7 .  FIG. 7  is a flow chart explaining steps of the random access method according to Embodiment 2 of the present invention. 
         [0073]    First, in step ST 710 , priority determining section  601  determines a priority of radio communication terminal apparatus  600  based on QoS delay requirement information input from control section or the like (not shown). 
         [0074]    Subsequently, in step ST 720 , number-of-duplications determining section  602  determines the number of duplications of transmission packets according to the priority determined in step ST 710 , and inputs information of the number of duplications to duplication section  202 . 
         [0075]    Then, steps ST 310  to  340  in Embodiment 1 are to be sequentially executed. 
         [0076]    Here, an example of the conversion table held in number-of-duplications determining section  602  will be shown below in “Table 1.” This conversion table is made such that .alpha.=1, based on c=.alpha..times.p . . . (1) {c is the number of duplications, .alpha. is constant and p is the priority}. 
         [0000]    TABLE-US-00001 TABLE 1 Priority:Number of duplications 5:5 4:4 3:3 2:2 1:1 
         [0077]    In this way, according to the random access method of this embodiment, the number of duplications of transmission packet in duplication section  202  are determined according to kinds of services to be planned after an individual channel is established, and as QoS delay requirement out of a plurality radio communication terminal apparatuses  600  becomes more demanding so that it is possible to establish the individual channel to base station apparatus  100  in a short time. As a result, according to the random access method according to this embodiment, the problems of deterioration of communication quality, non-accessible state for communication and the like are made less likely to occur in the plurality of the whole radio communication terminal apparatuses  600  belonging to the same cell. 
       Example Embodiment 3 
       [0078]      FIG. 8  is a block diagram showing a configuration of radio communication terminal apparatus  800  according to Embodiment 3 of the present invention. Radio communication terminal apparatus  800  further includes number-of-duplications determining section  802  in radio communication terminal apparatus  200  explained in Embodiment 1. Radio communication terminal apparatus  800  includes many components to show the same function as in the components of radio communication terminal apparatus  200  so that such components are assigned the same reference numerals as in the components of radio communication terminal apparatus  200 , and explanations thereof will be omitted. 
         [0079]    Number-of-duplications determining section  802  compares information of the number of retransmissions input from control section or the like (not shown) with a conversion table provided in advance, determines the number of duplications corresponding to the number of retransmissions and inputs information of the determined number of duplications to duplication section  202 . In addition, “the number of retransmissions” in this embodiment is incremented every time all TS1 to TS5 shown in either of  FIGS. 4A to 4D  are transmitted. 
         [0080]    Next, the operations of radio communication terminal apparatus  800  will be explained using  FIG. 9 .  FIG. 9  is a flow chart explaining steps of a random access method according to this embodiment. 
         [0081]    First, in step ST 910 , number-of-duplications determining section  802  compares the number of retransmissions input with the conversion table provided in advance, determines the number of duplications of the transmission packet and inputs information of the determined number of duplications to duplication section  202 . 
         [0082]    Then, steps ST 310  to ST 340  in Embodiment 1 are to be sequentially executed. 
         [0083]    Here, an example of a conversion table held in number-of-duplications determining section  802  will be shown below in “Table 2.” This conversion table is made such that .beta.=1, based on c=F.times..beta. . . . (1) {c is the number of duplications, F is the number of retransmissions and .beta. is constant}. 
         [0000]    TABLE-US-00002 TABLE 2 Number of retransmissions:Number of duplications 5:6 4:5 3:4 2:3 1:2 
         [0084]    In this way, according to the random access method of this embodiment, the number of transmission packets transmitted from radio communication terminal  800  to base station apparatus  100  by RACH increases according to the number of retransmissions so that, out of a plurality of radio communication terminal apparatuses  800  belonging to the same cell, one with higher urgency is more likely to establish the individual channel to base station apparatus  100  in a short time. As a result, according to the random access method of this embodiment, the problems of deterioration of communication quality, non-accessible state for communication and the like are made less likely to occur in the plurality of the whole radio communication terminal apparatuses  800  belonging to the same cell. 
       Example Embodiment 4 
       [0085]      FIG. 10  is a block diagram showing a configuration of radio communication terminal apparatus  1000  according to Embodiment 4 of the present invention. Radio communication terminal apparatus  1000  further includes radio reception section  1001 , control information extracting section  1002  and number-of-duplications determining section  1003  in radio communication terminal apparatus  200  explained in Embodiment 1. Radio communication terminal apparatus  1000  includes many components to show the same function as in the components of radio communication terminal apparatus  200  so that such components are assigned the same reference numerals as in the components of radio communication terminal apparatus  200 , and explanations thereof will be omitted. 
         [0086]    Radio reception apparatus  1001  includes bandpass filter, A/D converter, low noise amplifier, guard interval removal apparatus, S/P converter, FFT apparatus, P/S converter or the like, and acquires an OFDM signal to notify the number of radio communication terminal apparatus  1000  which belong to cell A transmitted regularly from base station terminal  100  through antenna element  223 , and after predetermined reception signal proceeding to the OFDM signal is performed, radio reception section  1001  inputs the OFDM signal to control information extracting section  1002 . 
         [0087]    Control information extracting section  1002  extracts information of the number of radio communication terminal apparatuses  1000  belonging to cell A out of the reception signal input from radio reception section  1001 , and inputs the extracted control information to number-of-duplications determining section  1003 . 
         [0088]    Number-of-duplications determining section  1003  compares control information input from control information extracting section  1002  with the conversion table provided in advance, determines the number of duplications corresponding to the control information and inputs the information of the determined number of duplications to duplication section  202 . 
         [0089]    Next, the operations of radio communication terminal apparatus  1000  will be explained using  FIG. 11 .  FIG. 11  is a flow chart explaining steps for a random access method according to this embodiment. 
         [0090]    First, in step ST 1110 , control information extracting section  1002  extracts control information from reception signal input from radio reception section  1001 . 
         [0091]    Then, in step ST 1120 , number-of-duplication determining section  1003  learns the number of radio communication terminal apparatuses  1000  belonging to cell A based on control information and determines the number of duplications corresponding to this number with reference to the conversion table provided in advance. 
         [0092]    Steps ST 310  to ST 340  in Embodiment 1 are to be sequentially executed. 
         [0093]    Here, an example of the conversion table held in number-of-duplications determining section  1003  will be shown below in “Table 3.” In table 3, RACH subchannel assigning section  211  is taken to process a total of 1000 RACH subchannels composed of 10 time slots and 100 subcarriers per time slot as a RACH unit, assign 100 transmission packets at maximum in one unit and furthermore, radio communication terminal apparatus  1000  belongs to priorities 1 to 5. 
         [0000]    TABLE-US-00003 TABLE 3 Priority/Number of duplications (number of terminals)/(20):(35):(100) 5/7(4):5(7):1(20) 4/6(4):4(7):1(20) 3/5(4):3(7):1(20) 2/4(4):2(7):1(20) 1/1(4):1(7):1(20) Sum of the number of duplications: 92:98:100 
         [0094]    Furthermore, in  FIG. 12A , correlation between the number of radio communication terminal apparatuses  1000  belonging to cell A and the number of duplications about priority 5 in this embodiment is shown. Also, in  FIG. 12B , correlation between the number of radio communication terminal apparatuses  1000  belonging to cell A and the number of duplications about priority 3 in this embodiment is shown. As shown in  FIG. 12A  and  FIG. 12B , this embodiment is set such that the number of duplications of transmission packet in duplication section  202  decreases with increase of the number of radio communication terminal apparatuses  1000  belonging to the same cell. 
         [0095]    Therefore, according to the random access method of this embodiment, as the number of radio communication terminal apparatuses  1000  belonging to the same cell increases, the number of transmission packets transmitted by radio communication terminal apparatuses  1000  decreases so that it is possible to reduce the likelihood of collision of transmission packets at RACH in the same cell. As a result, according to the random access method according to this embodiment, the problems of deterioration of communication quality, non-accessible state for communication and the like are made less likely to occur in the plurality of the whole radio communication terminal apparatuses  1000  belonging to the same cell. 
         [0096]    In addition, although in the above embodiments, a case has been described where the duplicated transmission packets are multiplexed and transmitted in subcarriers or time slots, when, for example, other resources such as radio communication terminal apparatus  200  include a plurality of transmission antennas, it is possible to multiplex and transmit the duplicated transmission packets in spatial resources such as transmission antenna and directivity pattern, and spreading codes in CDMA system. 
         [0097]    In addition, function blocks used in the explanations of the above embodiments are typically implemented as LSI constituted by an integrated circuit. These may be individual chips or partially or totally contained on a single cup. 
         [0098]    “LSI” is adopted here but this may also be referred to as “IC,” “system LSI,” “super LSI,” or “ultra LSI” depending on differing extents of integration. 
         [0099]    Further, the method of circuit integration is not limited to LSI&#39;s, and implementation using dedicated circuitry or general purpose processors is also possible. After LSI manufacture, utilization of an FPGA (Field Programmable Gate Array) or a reconfigurable processor where connections and settings of circuit cells within an LSI can be reconfigured is also possible. 
         [0100]    Further, if integrated circuit technology comes out to replace LSI&#39;s as a result of the advancement of semiconductor technology or a derivative other technology, it is naturally also possible to carry out function block integration using this technology. Application in biotechnology is also possible. 
         [0101]    The present application is based on Japanese Patent Application No. 2004-065625 filed on Mar. 9, 2004, the entire content of which is expressively incorporated by reference herein. 
       INDUSTRIAL APPLICABILITY 
       [0102]    The random access method and radio communication terminal apparatus according to the present invention provides an advantage of establishing an individual channel to the base station in a short time, and is effective for using in the radio communication system and the like with service demanding QoS delay requirement planned.