Abstract:
Provided are a packet transmission device and a packet transmission method which can effectively use a radio band while suppressing a processing overhead. A packet transmission device ( 100 ) includes: a transmission path judgment unit ( 110 ) which judges a transmission path state according to a radio channel quality estimation result; and an adaptive scheduler unit ( 108 ) which includes a low QoS packet into a transmission frame constituent element with a higher priority if the transmission path state is judged to be bad and a high QoS packet into the transmission frame constituent element with a higher priority if the transmission path state is judged to be good. That is, the adaptive scheduler unit ( 108 ) allocates a low QoS packet with a higher priority when it is judged that the possibility of generation of a radio error is high and the transmission path state is bad.

Description:
TECHNICAL FIELD 
       [0001]    The present invention relates to a packet transmitting apparatus and a packet transmitting method for digital mobile communication to allow packet communication. 
       BACKGROUND ART 
       [0002]    Conventionally, in the field of radio communication systems, a communication scheme referred to as “HSDPA” has been standardized whereby a plurality of communication terminal apparatuses share high speed and large capacity downlink channels to perform high-speed packet transmission in the downlink, besides communication schemes that performs transmission to communication terminal apparatuses using DPCHs (dedicated physical channels). 
         [0003]    In radio communication, propagation conditions are significantly unstable, and the capacity of communication channels widely changes over time. HSDPA (High Speed Downlink Packet Access) uses this. HSDPA is a technique of performing high-speed transmission using M-ary modulation and low coding rate when communication conditions are good, in order to improve peak throughput. 
         [0004]    In this HSDPA system, a base station apparatus has signals referred to as “CQIs (channel quality indicators)” transmitted from communication terminal apparatuses, where CQIs indicate modulation schemes and coding rates of packet data that can be demodulated in communication terminal apparatuses. Upon receiving a CQI, the base station apparatus performs scheduling using the CQI transmitted from each communication terminal apparatus and selects the optimal modulation scheme, coding rate and so forth. Then, the base station apparatus modulates and encodes transmission data using the selected modulation scheme, coding rate and so forth, and transmits data to each communication terminal apparatus, based on the scheduling result. By this means, transmission rates are adaptively changed depending on radiowave propagation environments, so that HSDPA makes it possible to transmit a larger capacity of data from a base station apparatus to communication terminal apparatuses than DPCH. 
         [0005]    In addition, in this HSDPA system, communication terminal apparatuses transmit an ACK/NACK signal indicating whether or not a downlink packet referred to as “HS-PDSCH (high speed physical downlink shared channel)” could be received, and CQI signals over an HS-DPCCH (dedicated physical control channel (uplink) for HS-DSCHs.) With this method, an HS-DPCCH is code-multiplexed with a DPCCH (dedicated physical control channel) and a DPDCH (dedicated physical data channel), and transmitted. 
         [0006]    A transmitter in digital mobile communication to allow packet communication generates radio errors, including possible fading in radio channels; a frequency error due to Doppler frequency that may be caused by movement of a mobile device; deterioration of receiving sensitivity that may be caused by being away from a base station. By these radio errors, cases might occur where a receiver cannot correctly decode a radio frame transmitted from a transmitter and obtain a packet contained in the radio frame. 
         [0007]    A HARQ (Hybrid ARQ) technique is a retransmission scheme in which, when a radio frame that could not be correctly decoded as described above is detected, a retransmission request is made to the transmitter side and the radio frame that could not be decoded is held in the receiver side, and then, when a radio frame retransmitted from the transmitter is received, the held radio frame received last time and that retransmitted frame are combined, and reinforced with redundant bits to decode the radio frame. In the field of digital mobile communication, HARQ has been adopted in digital mobile telephone standards to allow high-speed packet communication, and is being adopted, for example, in mobile telephones in compliance with the HSPA standard centered around Japan and also in mobile telephones in compliance with the EDGE standard centered around Europe. In addition, HARQ is due to be adopted in the next generation high-speed packet communication standard 3G-LTE (Long Term Evolution), standardization of which is underway. 
         [0008]    The above-described HARQ technique is essential to realization of high-speed packet communication. A radio frame decoding failure due to a radio error creates a problem that a huge amount of processing time is required to perform a sequential additional processing, including transmission processing to make retransmission request from a receiver to a transmitter; retransmission frame construction processing upon receiving the retransmission request; retransmission processing to retransmit from the transmitter; and reception processing upon receiving a retransmission frame. 
         [0009]    To address the above-described problem of processing time, it has been proposed to reduce frequency of occurrence of retransmissions requiring processing time by adjusting transmission timings depending on the moving speed of a mobile device and by performing asynchronous transmission depending on radio channel conditions when the mobile device moves at a low speed (for example, see Patent Literature 1.) However, if a radio channel condition is poor, it is anticipated that radio bands are wasted and synchronization processing overhead due to asynchronous transmission increases. 
         [0010]      FIG. 1  is a block diagram showing a configuration of a conventional packet transmitting apparatus. 
         [0011]    In  FIG. 1 , packet transmitting apparatus  10  has RF processing section  11 , baseband processing section  12 , retransmission control section  13 , retransmission buffer section  14 , frame analysis section  15 , reception buffer sections  16 - 1  to  16 -N, frame assembling section  17 , scheduler section  18 , and transmission buffer sections  19 - 1  to  19 -N. 
         [0012]    RF processing section  11  converts a digital signal radio frame to an analog signal radio frame, and sends the result from radio antenna  11   a  by radio. In addition, RF processing section  11  converts an analog signal radio frame transmitted by radio to a digital signal radio frame. 
         [0013]    Baseband processing section  12  performs demodulation and decoding processing on a received signal having been converted to a radio frame by RF processing section  11 , and outputs a transmission packet delivery acknowledgement signal and a received packet from a counterpart receiving apparatus, which are obtained by the demodulation and decoding processing, to retransmission control section  13 . In addition, baseband processing section  12  performs coding and modulation processing on a transmission radio frame outputted from retransmission control section  13 , and transmits the result via RF processing section  11  by radio. 
         [0014]    Retransmission control section  13  sends a transmission radio frame from frame assembling section  17 , or, when a retransmission request is made, sends a retransmission radio frame from retransmission buffer section  14  to baseband processing section  102  at the time the retransmission radio frame should be transmitted, and holds it in retransmission buffer section  14  until receiving a delivery acknowledgement from a counterpart receiver. 
         [0015]    Frame analysis section  15  analyzes protocol header information of a radio frame to store a received packet and specifies the position and logical channel information of the received packet. 
         [0016]    Reception buffer sections  16 - 1  to  16 -N accumulate received packets specified in frame analysis section  15 , in association with logical channel information. 
         [0017]    Frame assembling section  17  assembles a radio frame in accordance with a frame format, based on transmission frame components determined in the above scheduler section. 
         [0018]    Scheduler section  18  determines transmission frame components from the above transmission buffer sections, based on a scheduling method. 
         [0019]    Transmission buffer sections  19 - 1  to  19 -N accumulate transmission packets associated with service quality (QoS.) 
         [0020]      FIG. 2  is a drawing explaining packet transmission delay time when the above packet transmitting apparatus  10  is applied. In  FIG. 2 , numbers on the horizontal axis represent radio frames transmitted from a transmission source transmitter, and radio frames received by a reception source receiver. 
         [0021]    In  FIG. 2 , packets are transmitted from a transmission source transmitter (packet transmitting apparatus  10 ) having the configuration shown in  FIG. 1 . 
         [0022]    As shown in  FIG. 2   a ., when a radio error occurs in a fifth radio frame, the counterpart reception source receiver side detects occurrence of the radio error (see  FIG. 2   b .). The reception source receiver reports the detection result to a reception source transmitter (see  FIG. 2   c .), and then the reception source transmitter generates and transmits NACK information (see  FIG. 2D .). 
         [0023]    A transmission source receiver detects the NACK information (see  FIG. 2   e .), and reports the detection result to a transmission source transmitter (see  FIG. 2   f .). Upon receiving this, the transmission source receiver retransmits the fifth radio frame in which a radio error has occurred (see  FIG. 2   g .). 
         [0024]    The reception source transmitter recognizes that a delivery failure has occurred in the above process. This process includes a radio transmission delay (see  FIG. 2   h .) to transmit radio frames from the transmission source to the reception source receiver, and a processing delay in the reception source (see  FIG. 2   i .) in order that the reception source receiver receives radio frames, performs demodulation and decoding processing, reports the error detection result to the reception source receiver, generates NACK information and performs coding and modulation processing. In addition, there are a transmission delay (see  FIG. 2   j .) to transmit radio frames containing NACK information from the reception source transmitter transmits to transmission source transmitter, and a processing delay in the transmission source (see  FIG. 2   k .) in order that the transmission source receiver receives radio frames, performs demodulation and decoding processing, detects NACK information and reports the detection result to the transmission source transmitter. These processing delays are totalized, and in addition, when transmission is performed at the timing in synchronization with the reception source side, a waiting time to wait for the synchronized timing (see  FIG. 2   l .) is added. 
       Citation List 
     Patent Literature 
     [PTL 1] 
       [0000]    
       
         Patent 2007-318764 
       
     
       SUMMARY OF INVENTION 
     Technical Problem 
       [0026]    However, with this conventional packet transmitting apparatus, when radio communication conditions are poor, it is anticipated that radio bands are wasted, and synchronization processing overhead due to asynchronous transmission increases. 
         [0027]    In addition, when a mobile terminal is supposed to process services requiring low delay typified by VoIP voice call and process services requiring high transmission rate typified by FTP download at the same time, there is a problem to be solved to assure the quality at the time of occurrence of retransmission under a poor transmission channel condition, that is, to allow high transmission rate with low delay. 
         [0028]    It is therefore an object of the present invention to provide a packet transmitting apparatus and a packet transmitting method to allow efficient use of radio bands while reducing processing overhead. 
       Solution to Problem 
       [0029]    The packet transmitting apparatus according to the present invention adopts a configuration to include: a transmission buffer section that accumulates transmission packets associated with service quality (QoS); a baseband processing section that estimates radio channel quality by demodulation and decoding processing; a transmission channel judgment section that judges a transmission channel condition, based on a radio channel quality estimation result from the baseband processing section; an adaptive scheduler section that selects one of a plurality of scheduling methods based on the transmission channel condition from the transmission channel judgment section, and determines transmission frame components in transmission packets accumulated in the transmission buffer section; a frame assembling section that assembles a radio frame in compliance with a frame format, based on the transmission frame components determined in the adaptive scheduler section; and a retransmission control section that sends a transmission radio frame from the frame assembling section, or, when a retransmission request is made, sends a retransmission radio frame from a retransmission buffer to the baseband processing section, and holds the transmission radio frame or the retransmission radio frame in the retransmission buffer until receiving a delivery acknowledgement from a counterpart receiver. When the transmission channel judgment section judges that the transmission channel condition is poor, the adaptive scheduler section preferentially includes a low service quality packet in the transmission frame components, and, when the transmission channel judgment section judges that the transmission channel condition is good, preferentially includes a high service quality packet in the transmission frame components. 
         [0030]    The packet transmitting method according to the present invention includes the steps of: accumulating transmission packets associated with service quality; estimating radio channel quality by demodulation and decoding processing; judging a transmission channel condition based on an estimation result of the radio channel quality; selecting one of a plurality of scheduling methods based on the transmission channel condition and determining transmission frame components of the transmission packets accumulated, based on the selected scheduling method; assembling a radio frame in compliance with a frame format based on the determined transmission frame components; and sending a transmission radio frame, or, when a retransmission request is made, sending a retransmission radio frame, and holding the transmission frame or the retransmission frame in the retransmission buffer until a delivery acknowledgement is received from a counterpart receiver. When the transmission channel condition is judged to be poor, a low service quality packet is preferentially included in transmission frame components, and, when the transmission channel condition is judged to be good, a high service quality packet is preferentially included in the transmission frame components. 
       Advantageous Effects of Invention 
       [0031]    According to the present invention, when a transmission channel conditions is judged to be poor, low QoS packets are preferentially included in transmission frame components, and, on the other hand, when a transmission channel condition is judged to be good, high QoS packets are preferentially included in transmission frame components. By this means, it is possible to prevent increase in delay time until high QoS packets arrive and prevent deterioration of communication quality due to radio errors, and also realize a packet transmitting apparatus to keep the transmission rate of low QoS packets. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0032]      FIG. 1  is a block diagram showing a configuration of a conventional packet transmitting apparatus; 
           [0033]      FIG. 2  is a drawing explaining packet transmission delay time when the conventional packet transmitting apparatus is applied; 
           [0034]      FIG. 3  is a block diagram showing a configuration of a packet transmitting apparatus according to Embodiment  1  of the present invention; 
           [0035]      FIG. 4  shows a circuit configuration of a simplified transmission channel judgment section in the packet transmitting apparatus according to Embodiment 1; 
           [0036]      FIG. 5  shows a circuit configuration of a high-precision transmission channel judgment section in the packet transmitting apparatus according to Embodiment 1; 
           [0037]      FIG. 6  shows a circuit configuration of the simplified transmission judgment section with the number of times of retransmissions control in the packet transmitting apparatus according to Embodiment 1; 
           [0038]      FIG. 7  shows a circuit configuration of the high-precision transmission channel judgment section with control of the number of times of retransmissions in the packet transmitting apparatus according to Embodiment 1; 
           [0039]      FIG. 8  shows a configuration of a simplified adaptive scheduler section in the packet transmitting apparatus according to Embodiment 1; 
           [0040]      FIG. 9  shows a circuit configuration of a duplicate transmission in the packet transmitting apparatus according to Embodiment 1; 
           [0041]      FIG. 10  is a drawing explaining packet transmission delay time when the packet transmitting apparatus according to Embodiment 1 is applied; 
           [0042]      FIG. 11  is a block diagram showing a configuration of a packet transmitting apparatus according to Embodiment 2 of the present invention; and 
           [0043]      FIG. 12  is a drawing explaining packet transmission delay time when the packet transmitting apparatus according to Embodiment 2 is applied. 
       
    
    
     DESCRIPTION OF EMBODIMENTS 
       [0044]    Now, embodiments of the present invention will be described in detail with reference to the accompanying drawings. 
       Embodiment 1 
       [0045]      FIG. 3  is a block diagram showing a configuration of a packet transmitting apparatus according to Embodiment 1 of the present invention. The present embodiment is an example of a case in which the packet transmitting apparatus is a digital mobile communication apparatus. 
         [0046]    In  FIG. 3 , packet transmitting apparatus  100  is configured to include RF processing section  101 , baseband processing section  102  (abbreviated as “PHY” in  FIG. 3 ), retransmission control section  103  (abbreviated as “HARQ” in  FIG. 3 ), retransmission buffer section  104 , frame analysis section  105 , reception buffer sections  106 - 1  to  106 -N, frame assembling section  107 , adaptive scheduler section  108 , transmission buffer sections  109 - 1  to  109 -N and transmission channel judgment section  110 . 
         [0047]    RF processing section  101  converts a digital signal radio frame to an analog signal radio frame, and sends the result from radio antenna  101   a  by radio. In addition, RF processing section  101  converts an analog signal radio frame by radio to a digital signal radio frame. 
         [0048]    Baseband processing section  102  performs demodulation and decoding processing on the received signal having been converted to a radio frame by RF processing section  101 , and outputs a transmission packet delivery acknowledgement signal and a received packet from a counterpart receiving apparatus, which are obtained by the demodulation and decoding processing, to retransmission control section  103 . In addition, baseband processing section  102  performs coding and modulation processing on a transmission radio frame outputted from retransmission control section  103 , and transmits the result via RF processing section  101  by radio. In addition, baseband processing section  102  estimates radio channel quality by modulation and decoding processing and outputs the radio channel quality estimation result to transmission channel judgment section  110 . 
         [0049]    Retransmission control section  103  sends a transmission radio frame from frame assembling section  107 , or, when a retransmission request is made, sends a retransmission radio frame from retransmission buffer section  104  to baseband processing section  102  at the time the retransmission radio frame should be transmitted, and holds it in retransmission buffer section  104  until receiving a delivery acknowledgment from a counterpart receiver. In addition, retransmission control section  103  outputs the radio channel quality estimation result to transmission channel judgment section  110 . 
         [0050]    Frame analysis section  105  analyzes protocol header information of a radio frame to store a received packet and specifies the position and logical channel information of the received packet. Frame analysis section  105  receives radio frames with no error from retransmission control section  103 , assign storage buffers based on information (e.g. channel ID) in frames and stores them in reception buffer sections  106 - 1  to  106 -N. 
         [0051]    Reception buffer sections  106 - 1  to  106 -N accumulate received packets having been specified in frame analysis section  105 , in association with logical channel information. 
         [0052]    Frame assembling section  107  assembles a radio frame in accordance with a frame format, based on transmission frame components determined by adaptive scheduler section  108 . 
         [0053]    Adaptive scheduler section  108  selects one of a plurality of scheduling methods, based on a transmission channel condition from transmission channel judgment section  110 , and determines transmission frame components of transmission packets accumulated in transmission buffer sections  109 - 1  to  109 -N, based on the selected scheduling method. A transmission frame component is a packet or part of a packet. Since packets are stored in transmission buffer sections  109 - 1  to  109 -N, packets themselves are transmission frame components. To be more specific, when transmission channel judgment section  110  judges that a transmission channel condition is poor, adaptive scheduler section  108  preferentially includes low QoS packets in transmission frame components, and, when transmission channel judgment section  110  judges that a transmission channel condition is good, preferentially includes high QoS packets in transmission frame components. The circuit configuration of adaptive scheduler section  108  will be described in detail later, with reference to  FIG. 8  and  FIG. 9 . 
         [0054]    Transmission buffer sections  109 - 1  to  109 -N accumulate transmission packets associated with service quality (QoS.) 
         [0055]    Transmission channel judgment section  110  judges transmission channel conditions, based on radio channel quality estimation results from baseband processing section  102  and retransmission frame information from retransmission control section  103 . The circuit configuration of transmission channel judgment section  110  will be described in detail as follows, with reference to  FIG. 4  to  FIG. 7 . 
         [0056]      FIG. 4  shows a circuit configuration of a simplified transmission channel judgment section  110 . Simplified transmission channel judgment section  200  is used as a simple version of transmission channel judgment section  110  in  FIG. 3 . 
         [0057]    In  FIG. 4 , simplified transmission channel judgment section  200  includes comparator  201 . 
         [0058]    Comparator  201  compares received bit error rate estimation value  202  of radio channel quality estimation results from baseband processing section  102  ( FIG. 3 ), with a preset threshold. 
         [0059]    When the bit error rate estimation value is greater than the preset threshold, simplified transmission channel judgment section  200  outputs an indication that the transmission channel condition is poor. 
         [0060]    This simplified transmission channel judgment section  200  can judge whether transmission channel conditions are good or poor with relatively a little amount of processing. 
         [0061]      FIG. 5  shows a circuit configuration of a high-precision transmission channel judgment section  110 . High-precision transmission channel judgment section  300  is used as a high-precision version of transmission channel judgment section  110  in  FIG. 3 . 
         [0062]    In  FIG. 5 , high-precision transmission channel judgment section  300  is composed of comparator  301  and selector  302 . Input port a in comparator  301  receives, as input, received power level estimation value  303  of radio channel quality estimation results from baseband processing section  102  ( FIG. 3 .) In addition, input port b in comparator  301  receives a threshold selected by selector  302  as input. 
         [0063]    Selector  302  selects an appropriate threshold from thresholds  1 ,  2 , . . . , N that are preset every certain frequency error estimation value range, based on frequency error estimation value  304  inputted. 
         [0064]    Comparator  301  compares received power level estimation value  303  with the threshold selected by selector  302 . 
         [0065]    As described above, in high-precision transmission channel judgment section  300 , selector  302  selects the threshold from frequency error estimation value  304 , and, when received power level estimation value  303  is lower than the selected threshold, comparator  301  outputs an indication that the transmission channel condition is poor. 
         [0066]    This high-precision transmission channel judgment section  300  can judge precisely whether transmission channel conditions are good or poor more than simplified transmission channel judgment section  200  in  FIG. 4 . 
         [0067]    Reception sensitivity of a mobile device varies, for example, when a mobile device does not move, moves and moves fast. The reception power level threshold is changed using a frequency error due to Doppler frequency caused by the moving speed of a mobile device as frequency error estimation value  304 . By this means, it is possible to judge more precisely whether transmission channel conditions are good or poor. 
         [0068]      FIG. 6  is a circuit configuration of simplified transmission channel judgment section  110  with control of the number of times of retransmissions. Simplified transmission channel judgment section  400  with control of the number of times of retransmissions is used as simplified transmission channel judgment section  110  with control of the number of times of retransmissions shown in  FIG. 3 . 
         [0069]    In  FIG. 6 , simplified transmission channel judgment section  400  with control of the number of times of retransmissions is composed of comparator  401  and selector  402 . Input port a in comparator  401  receives, as input, bit error rate estimation value  403  of radio channel quality estimation results from baseband processing section  102  ( FIG. 3 .) In addition, input port b in comparator  401  receives a threshold selected by selector  402  as input. 
         [0070]    Selector  402  selects an appropriate threshold from thresholds  1 ,  2 , . . . , N preset by the number of times of retransmissions, based on the number of times of retransmissions  404  from retransmission control section  103  ( FIG. 3 .) 
         [0071]    Comparator  401  compares bit error rate estimation value  403  with the threshold selected by selector  402 . 
         [0072]    As described above, in simplified transmission channel judgment section  400  with control of the number of times of retransmissions, selector  402  selects thresholds according to the number of times of retransmissions  404 , and, when bit error rate estimation value  403  is greater than the selected threshold, comparator  401  outputs an indication that the transmission channel condition is poor. 
         [0073]    HARQ is a technique to maximally derive coding gain by combining retransmission data with past transmission data accumulated in a counterpart receiver side, reinforcing redundancy and decoding the result, and therefore provides improved radio error robustness because of reinforcing redundancy at the time of retransmission. This allows delivery at the time of retransmission even if the transmission channel condition is poorer than at the time of the first transmission, and it is possible to reduce delay time until arrival more than in simplified transmission channel judgment section  200  in  FIG. 4  by setting a threshold so as to increase the threshold according to the number of times of retransmissions  404 . 
         [0074]      FIG. 7  shows a circuit configuration of high-precision transmission channel judgment section  110  with control of the number of times of retransmissions. High-precision transmission channel judgment section  500  with control of the number of times of retransmissions is used as a high-precision version of transmission channel judgment section  110  in  FIG. 3 , with control of the number of times of retransmissions. High-precision transmission channel judgment section  500  with control of the number of times of retransmissions has a configuration by combining high-precision transmission channel judgment section  300  in  FIG. 5  and simplified transmission channel judgment section  400  with control of the number of times of retransmissions in  FIG. 6 . 
         [0075]    In  FIG. 7 , high-precision transmission channel judgment section  500  with control of the number of times of retransmissions is configured to include comparator  501 , selector  502  and retransmission count control selector  503 . Input port a in comparator  501  receives, as input, received power level estimation value  504  of radio channel quality estimation results from baseband processing section  102  ( FIG. 3 .) In addition, input port b in comparator  501  receives a threshold selected by selector  502  as input. 
         [0076]    Retransmission count control selector  503  is composed of selector  511  that selects an appropriate threshold from thresholds  1 - 1 ,  1 - 2 , . . . ,  1 -M, selector  512  that selects an appropriate threshold from thresholds  2 - 1 ,  2 - 2 , . . . ,  2 -M and selector  513  that selects an appropriate threshold from thresholds N- 1 , N- 2 , . . . , N-M. 
         [0077]    Retransmission count control selector  503  selects an appropriate threshold from thresholds preset by the number of times of retransmissions every certain frequency error estimation value range, based on the number of retransmissions  506  from retransmission control section  103  ( FIG. 3 .) 
         [0078]    Selector  502  selects an appropriate threshold from a group of thresholds selected by retransmission count control selector  503 , based on frequency error estimation value  505  inputted. For example, when retransmission count control selector  503  selects selector  511  based on the number of times of retransmissions  506 , selector  502  selects an appropriate threshold (e.g. threshold  1 - 2 ), among thresholds  1 - 1 ,  1 - 2 , . . . ,  1 -M for selector  511 , which are selected by retransmission count control selector  503 . 
         [0079]    Comparator  501  compares received power level estimation value  503  with the threshold selected by selector  502 . 
         [0080]    As described above, in high-precision transmission channel judgment section  500  with control of the number of times of retransmissions, retransmission count control selector  503  selects an appropriate threshold from thresholds preset by the number of times of retransmissions according to the number of times of retransmissions  506 , every certain frequency error estimation value range; selector  502  selects an appropriate threshold from a group of thresholds selected by retransmission count control selector  503 , based on frequency error estimation value  505  inputted; and, when received power level estimation value  503  is lower than the selected threshold, comparator  501  outputs an indication that the channel condition is poor. 
         [0081]    Therefore, this high-precision transmission channel judgment section  500  with control of the number of times of retransmissions is expected to produce the same effect as in simplified transmission channel judgment section  400  with control of the number of times of retransmissions in  FIG. 6 , and is able to reduce delay time until arrival more than high-precision transmission channel judgment section  300  in  FIG. 5 . 
         [0082]    The circuit configuration of transmission channel judgment section  110  has been described in detail. Next, a circuit configuration of adaptive scheduler section  108  will be described in detail. 
         [0083]      FIG. 8  shows a configuration of a simple version of the above-described adaptive scheduler section  108 . Simplified adaptive scheduler section  600  is used as a simple version of adaptive scheduler section  108  in  FIG. 3 . 
         [0084]    In  FIG. 8 , simplified adaptive scheduler section  600  is composed of scheduler adapter  601 , high QoS packet preferential scheduler section  602  and low QoS packet preferential scheduler section  603 . In addition, transmission channel condition signal  604  is inputted to scheduler adapter  601 . 
         [0085]    Scheduler adapter  601  selects output from high QoS packet preferential scheduler section  602  or output from low QoS packet preferential scheduler section  603 , based on transmission channel condition signal  604 . 
         [0086]    High QoS packet preferential scheduler section  602  schedules transmission buffer sections  109 - 1  to  109 -N ( FIG. 3 ) in the order of priority from a transmission buffer section to store a transmission packet associated with a higher QoS service. 
         [0087]    Low QoS packet preferential scheduler section  603  schedules transmission buffer sections  109 - 1  to  109 -N ( FIG. 3 ) in the order of priority from a transmission buffer section to store a transmission packet associated with a lower QoS service. 
         [0088]    When transmission channel conditions are poor, this simplified adaptive scheduler section  600  can select output from low QoS packet preferential scheduler section  603 . This simplified adaptive scheduler  600  has an advantage of allowing adaptive scheduling processing with relatively a little amount of processing. 
         [0089]      FIG. 9  shows a circuit configuration of a duplicate transmission version of the above-described adaptive scheduler section  108 . Duplicate transmission adaptive scheduler section  700  is used as a duplicate transmission version of adaptive scheduler section  108  in  FIG. 3 . Here, duplicate transmission adaptive scheduler section  700  has a circuit configuration specific to Embodiment 2 described later (noted here for convenience of explanation.) 
         [0090]    In  FIG. 9 , duplicate transmission adaptive scheduler section  700  is composed of scheduler adapter  701 , high QoS packet preferential scheduler section  702  and sequential transmission packet preferential scheduler section  703 . In addition, scheduler adapter  701  receives, as input, transmission channel condition signal  704  and sequential transmission buffer evacuation packet delivery acknowledgement signal  705 . Sequential transmission packet preferential scheduler section  703  is connected to the outside via communication interface  706 . 
         [0091]    When a transmission channel condition is judged to be poor based on transmission channel condition signal  704 , scheduler adapter  701  switches to output of sequential transmission packet scheduler section  703 . In addition, at the time of receiving delivery acknowledgement for an evacuating transmission packet to a plurality of transmission buffers  811  (see  FIG. 11  described later), based on sequential transmission buffer evacuation packet delivery acknowledgment signal  705  from retransmission control section  103  ( FIG. 3 ), scheduler adapter  701  switches to high QoS packet preferential scheduler section  702 . 
         [0092]    High QoS packet preferential scheduler section  702  schedules transmission buffer sections  109 - 1  to  109 -N ( FIG. 3 ) in the order of priority from a transmission buffer section to store a transmission packet associated with a higher QoS service. 
         [0093]    Sequential transmission packet preferential scheduler section  703  schedules transmission packets in the order of priority from a transmission packet stored in a sequential transmission buffer (not shown) and evacuates the first transmission packet, among transmission packets associated with preset high QoS services, to the sequential transmission buffer (not shown.) 
         [0094]    As described above, scheduler adapter  701  is an adaptive scheduling section that selects output of sequential transmission packet preferential scheduler section  703  when transmission channel conditions are poor. Transmission channel judgment section  103  ( FIG. 3 ) cannot always accurately judge transmission channels. Even if transmission channel judgment section  103  judges that a transmission channel condition is poor, a case is possible where there is no radio error, and in this case, only high QoS service packets are delayed. 
         [0095]    In order to prevent this event, even if a transmission channel condition is judged to be poor, high QoS service packets are preferentially scheduled. The same high QoS service packet is redundantly transmitted every transmission opportunity until delivery acknowledgement is received because a radio error is highly likely to occur. By this means, it is possible to reduce delay time until arrival. 
         [0096]    However, the same packet can redundantly arrive at the receiver side, so that a duplicate packet discarding mechanism is essential in the receiver side. This is processing is prepared in general HARQ retransmission control because unintended retransmission is likely to occur when a delivery acknowledgement signal has a radio error (although an ACK signal is transmitted from the receiver side, the signal is construed as a NACK signal due to a radio error). 
         [0097]    Now, operations of the packet transmitting apparatus configured as described above will be explained. 
         [0098]    Packet transmitting apparatus  100  according to the present embodiment is characterized by having adaptive scheduler section  108  and transmission channel judgment section  110 . In addition, adaptive scheduler section  108  uses simplified adaptive scheduler section  600  in  FIG. 8 , or duplicate transmission adaptive scheduler section  700  in  FIG. 9 . Transmission channel judgment section  110  uses one of transmission channel judgment sections in  FIG. 4  to  FIG. 7 . 
         [0099]    In  FIG. 3 , baseband processing section  102  receives a received signal converted to a digital baseband signal, as input, to estimate radio channel quality. 
         [0100]    Transmission channel judgment section  110  judges a transmission channel condition, based on the radio channel quality estimation result from baseband processing section  102 . 
         [0101]    Adaptive scheduler section  108  selects one of a plurality of scheduling methods, based on the transmission channel condition from transmission channel judgment section  110 , and determines transmission frame components. When the transmission channel condition is judged to be poor, adaptive scheduler section  108  preferentially includes low QoS packets in transmission frame components, and, when the transmission channel condition is judged to be good, preferentially includes high QoS packets in transmission frame components. 
         [0102]    Now, different characteristics and points of adaptive scheduler section  108  from conventional scheduler section  18  ( FIG. 1 ) will be explained. 
         [0103]    (1) In the conventional example, scheduler section  18  ( FIG. 1 ) does not take into account transmission channel conditions and has one scheduling algorithm. By contrast with this, adaptive scheduler section  108  selects one of a plurality of scheduling methods, based on the transmission channel condition from transmission channel judgment section  110  and determines transmission frame components. 
         [0104]    (2) When the transmission channel condition is judged to be poor, adaptive scheduler section  108  preferentially includes low QoS packets in transmission frame components. To be more specific, as shown in following  FIG. 10 , adaptive scheduler section  108  randomly delays transmission timings when transmission channel conditions are poor. Here, the relationship between “preferentially including low QoS packets in transmission frame components” and “randomly delaying transmission timings” will be explained. An object of the present invention is to provide high QoS maintaining high throughput while minimizing radio errors. Even if a low QoS packet has a radio error, it is possible to minimize the sacrifice of throughput by saving the low QoS packet by HARQ later. In addition, high QoS packets are controlled not to have an error even by randomly delaying high QoS packets. 
         [0105]    (3) Transmission timing delay is determined from a following viewpoint. That is, there is a certain level of correlation between a transmission channel condition such as Doppler frequency, and a BER (bit error rate), and, if the transmission channel condition exceeds a certain threshold (is improved), transmission is performed (that is, held until successful transmission is possible.) Assume that control factors are not only transmission channel conditions but also QoS desired to be transmitted, the present invention is characterized in that there are packets influenced and packets not influenced from transmission channel conditions, so that it is possible to maintain both QoS and throughput. 
         [0106]      FIG. 10  is a drawing explaining packet transmission delay time when the above-described packet transmitting apparatus  100  is applied. In  FIG. 10 , numbers on the horizontal axis represent radio frames transmitted from a transmission source transmitter, and radio frames received by a reception source receiver. 
         [0107]    In  FIG. 10 , the transmission source transmitter (packet transmitting apparatus  100 ) having the configuration shown in  FIG. 3  transmits packets. 
         [0108]    As shown in  FIG. 10   a ., when transmission channel judgment section  110  judges that a transmission channel condition is poor, adaptive scheduler section  108  judges that a radio error is highly likely to occur and preferentially assigns a low QoS packet. In a case shown in  FIG. 10 , when transmission channel judgment section  110  judges that a radio error is likely to occur in a fifth radio frame, adaptive scheduler section  108  holds the transmission of the fifth radio frame, transmits (see  FIG. 10   b .) a sixth radio frame formed by a lower QoS packet than the highest QoS packet of the fifth radio frame, and transmits (see  FIG. 10   c .) the fifth radio frame at the next synchronous transmission timing at which the transmission channel condition is improved. 
         [0109]    In this process, the total delay time is composed of a radio transmission delay (see  FIG. 10   h .) to transmit radio frames from the transmission source transmitter to the reception source receiver and a waiting time until the transmission channel condition is improved, and is shorter than in a case in which the conventional packet transmitting apparatus shown in  FIG. 2  is used. 
         [0110]    That is, in the process according to the present embodiment, the fifth radio frame transmission is delayed as shown in  FIG. 10   a ., the sixth radio frame formed by a lower QoS packet than the highest QoS packet of the fifth radio frame is transmitted (see  FIG. 10   b .) and the fifth radio transmission frame is transmitted (see  FIG. 10   c .) at the next synchronous transmission timing at which the transmission channel condition is improved. As shown in  FIG. 10   c ., the fifth radio frame is transmitted at the next synchronous transmission timing at which the transmission channel condition is improved, following the sixth radio frame transmission timing. 
         [0111]    In the conventional example, the total processing delay time includes a radio transmission delay (see  FIG. 2   h .) to transmit radio frames from the transmission source transmitter to the reception source receiver because the next synchronous transmission timing is postponed to the timing of  FIG. 2   l . as shown in  FIG. 2   m .; a processing delay in the reception source (see  FIG. 2   i .) in order that the reception source receiver receives radio frames, performs demodulation and decoding processing, reports the error detection result to the reception source transmitter, generates NACK information and performs coding and modulation processing; a transmission delay (see  FIG. 2   j .) in order that the reception source transmitter transmits radio frames containing NACK information to the transmission source receiver; and a processing delay in the transmission source (see  FIG. 2   k .) in order that the transmission source receiver receives radio frames, performs demodulation and decoding processing, detects NACK information and reports the result to transmission source transmitter, and, a waiting time to wait for a synchronous timing is added to the total processing delay time when transmission is performed at the timing in synchronization with the reception source side (see  FIG. 2   l .). By contrast with this, with the present embodiment, since the fifth radio frame is immediately transmitted at the next synchronous transmission timing (see  FIG. 10   c .), the above-described total processing delay time and the waiting time are not involved in retransmission processing of the fifth radio frame, so that it is possible to prevent increase in delay time until high QoS packets arrive due to retransmission processing. In a case shown in  FIG. 10 , the total delay time includes a radio transmission delay to transmit radio frames from the transmission source transmitter to the reception source receiver and the waiting time until the transmission channel is improved, and it is possible to remarkably reduce transmission delay time in the poor radio transmission channel condition. 
         [0112]    As described above in detail, in packet transmitting apparatus  100  according to the present embodiment, transmission channel judgment section  110  judges a transmission channel conditions based on the channel quality estimation result, and, when the transmission channel condition is judged to be poor, adaptive scheduler section  108  preferentially include low QoS packets in transmission frame components, and, on the other hand, when the transmission channel condition is judged to be good, adaptive scheduler section  108  preferentially include high QoS packets in transmission frame components. That is, adaptive scheduler section  108  preferentially assigns low QoS packets when judging that a radio error is highly likely to occur and a transmission condition is poor, so that it is possible to prevent retransmission of high QoS packets and also prevent increase in delay time until high QoS packets arrive due to retransmission processing. By this means, it is possible to prevent increase in delay time until high QoS packets arrive and deterioration of communication quality due to radio errors, and it is possible to maintain a low QoS packet transmission rate. 
         [0113]    Then, in the feature, when a mobile terminal is anticipated that processes services requiring low delay typified by VoIP (Voice over Internet Protocol) voice call and processes services requiring high transmission rate typified by FTP (File Transfer Protocol) download at the same time, it is possible to assure the quality at the time of retransmission in a poor radio transmission channel condition, that is, it is possible to realize high transmission rate with low delay. 
       Embodiment 2 
       [0114]      FIG. 11  is a block diagram showing a configuration of a packet transmitting apparatus according to Embodiment 2 of the present invention. The same components as in  FIG. 3  are assigned the same reference numerals and overlapping descriptions will be omitted. 
         [0115]    In  FIG. 11 , packet transmitting apparatus  800  is configured to include RF processing section  101 , baseband processing section  102 , retransmission control section  803 , retransmission buffer section  104 , frame analysis section  105 , reception buffer sections  106 - 1  to  106 -N, frame assembling section  107 , adaptive scheduler section  808 , transmission buffer sections  109 - 1  to  109 -N, transmission channel judgment section  810  and multiple transmission buffers  811 . 
         [0116]    RF processing section  101  converts a digital signal radio frame to an analog signal radio frame and sends the result from radio antenna  101   a  by radio, and converts an analog signal radio frame by radio to a digital signal radio frame. By this means, baseband processing section  102  makes it possible to perform demodulation and decoding processing and receive transmission delivery acknowledgement signals and received packets from a counterpart receiving apparatus. 
         [0117]    Baseband processing section  102  (abbreviated as “PHY”) receives, as input, received signals having been converted to digital baseband signals, estimates radio channel quality, performs coding and modulation processing on transmission radio frames and transmits the result by radio. 
         [0118]    Retransmission control section  803  (abbreviated as “HARQ”) sends a transmission radio frame from frame assembling section  107 , or, when a retransmission request is made, sends a retransmission radio frame from retransmission buffer section  104  to baseband processing section  102  at the time the retransmission radio frame should be transmitted, and holds the retransmission radio frame in transmission buffer section  104  until receiving a delivery acknowledgment from a counterpart receiver. 
         [0119]    Frame analysis section  105  analyzes protocol header information of a radio frame in which a received packet is stored, and specifies the position and logical channel information of the received packet. 
         [0120]    Reception buffer sections  106 - 1  to  106 -N maintain and accumulate received packets having been specified in frame analysis section  105 , in association with logical channel information. 
         [0121]    Frame assembling section  107  assembles a radio frame in compliance with a frame format based on transmission frame components determined in adaptive scheduler section  808 . 
         [0122]    Adaptive scheduler section  808  determines whether or not to change to a multiple transmission preferential scheduling method, based on transmission channel conditions from transmission channel judgment section  810  to evacuate transmission packets to multiple transmission buffers  811 , and determines whether or not to change to a high QoS preferential scheduling method, based on delivery information from retransmission control section  803  and determines transmission frame components from transmission buffer sections  109 - 1  to  109 -N. Adaptive scheduler section  808  preferably adopts duplicate transmission adaptive scheduler section  700  shown in  FIG. 9 . 
         [0123]    Transmission buffer sections  109 - 1  to  109 -N maintain and accumulate transmission packets associated with service quality (QoS). 
         [0124]    Transmission channel judgment section  810  judges transmission channel conditions, based on radio channel quality estimation results from baseband processing section  102  and the number of times of retransmissions from retransmission control section  803 . Transmission channel judgment section  810  preferably adopts high-precision transmission channel judgment section  300  shown in  FIG. 5 , or high-precision transmission channel judgment section  500  with control of the number of times of retransmissions shown in  FIG. 7 . 
         [0125]    Now, operations of the packet transmitting apparatus configured as described above will be explained. 
         [0126]    Packet transmitting apparatus  800  according to the present embodiment is characterized by having adaptive scheduler section  808 , transmission channel judgment section  810  and multiple transmission buffers  811 . The basic operation of packet transmitting apparatus  800  is the same as in packet transmitting apparatus  100  shown in  FIG. 3 . The difference is that adaptive scheduler section  808  performs following control using multiple transmission buffers  811 . 
         [0127]    Adaptive scheduler  808  determines whether or not to change to a multiple transmission preferential scheduling method based on transmission channel conditions from transmission channel judgment section  810  to evacuate transmission packets to multiple transmission buffers  811 , and determines whether or not to change to a high QoS preferential scheduling method based on transmission information from retransmission control section  803  and determines transmission frame components from transmission buffer sections  109 - 1  to  109 -N. 
         [0128]      FIG. 12  is a drawing explaining packet transmission delay time when the above-described packet transmitting apparatus  800  is applied. In  FIG. 12 , numbers on the horizontal axis represent radio frames transmitted from a transmission source transmitter and radio frames received by a reception source receiver. 
         [0129]    In  FIG. 12 , packets are transmitted from the transmission source transmitter (packet transmitting apparatus  800 ) having the configuration shown in  FIG. 11 . 
         [0130]    As shown in  FIG. 12   a ., when transmission channel judgment section  810  judges that a transmission channel condition is poor, adaptive scheduler section  808  switches the scheduler algorithm to the multiple transmission preferential scheduling method. In a case in  FIG. 12 , when transmission channel judgment section  810  judges that a radio error is likely to occur in a fifth radio frame, adaptive scheduler section  808  switches the scheduler algorithm to the multiple transmission preferential scheduling method, transmits (see  FIG. 12   b .) a sixth radio frame formed by a lower QoS packet than the highest QoS packet of the fifth frame and redundantly allocate high QoS packets to radio frames following the fifth frame. That is, as shown in  FIG. 12   c ., the data part of a high QoS packet is copied to each subsequent frame. It is allowed that a plurality of packets (various kinds of QoS) are present in a radio frame. Therefore, only a high QoS packets among a plurality of packets is copied to each subsequent radio frame. 
         [0131]    A multiple mode refers to the multiple transmission preferential scheduling method. In addition, in the multiple mode, high QoS packets are redundantly allocated. 
         [0132]    Although with Embodiment 1, transmission timings are delayed at random, transmission timings are switched in the multiple mode. Now, the technical relationship, advantage and whether combination is possible, will be explained. 
         [0133]    Embodiment 1 represents an aspect in which delays stay within a certain level by randomly delaying. The present embodiment represents an aspect to ensure a reliable success even if throughput is reduced a little. Transmission channel estimation has limitations, and therefore an estimation error may occur. Therefore, the embodiment has arrived at continuing transmitting the same high QoS packet until the condition is improved. By this means, it is possible to expect that high QoS packets are delivered in early stages. 
         [0134]    By this means, when the transmission channel judgment section makes an error of judgment and a radio error does not occur, transmission is possible with the shortest delay including only transmission delay, and, even if a radio error occurs, transmission is possible with the same delay time as in  FIG. 10 . In addition, in order to efficiently use radio bands, generally a radio frame has a frame format to allow multiplexing a plurality of packets and multiplexing packet fragments by packet division, and multiplexing is possible such that only high QoS packets are copied to radio frames following the fifth radio frame in  FIG. 12 , and low QoS packets are not copied as in a conventional arrangement manner. 
         [0135]    The above description is illustration of preferred embodiments of the present invention and the scope of the invention is not limited to this. 
         [0136]    Although the names “packet transmitting apparatus” and “packet transmitting method” are used in the above-described embodiments for ease of explanation, “packet communication apparatus”, “mobile terminal”, “radio communication apparatus”, “adaptive transmitting method” and so forth are possible, naturally. 
         [0137]    In addition, with the above-described embodiments, although CPUs are used as an example for explanation, hardware, DSP and so forth may be used. 
         [0138]    Moreover, the type, the number, the connection method and so forth of each of circuit components constituting the above-described packet transmitting apparatus are not limited to the above-described embodiments. 
         [0139]    In addition, the above-explained packet transmitting method may be realized by a program to operate this packet transmitting method. This program is stored in a computer-readable storage medium. 
         [0140]    The disclosure of Japanese Patent Application No. 2008-167715, filed on Jun. 26, 2008, including the specification, drawings and abstract, is incorporated herein by reference in its entirety. 
       INDUSTRIAL APPLICABILITY 
       [0141]    The packet transmitting apparatus and packet transmitting method according to the present invention are used as part of packet transmission processing in mobile telephone for mobile communication. Particularly, in the EDGE scheme centered around Europe, the HSDPA scheme centered around Japan, and the 3G-LTE scheme for next generation mobile communication, it is possible to contribute to improve high QoS services that require high real time performance such as VoIP. 
       REFERENCE SIGNS LIST 
       [0000]    
       
           100 ,  800  packet transmitting apparatus 
           101  RF processing section 
           101   a  radio antenna 
           102  baseband processing section 
           103 ,  803  retransmission control section 
           104  retransmission buffer section 
           105  frame analysis section 
           106 - 1  to  106 -N reception buffer section 
           107  frame assembling section 
           108 ,  600 ,  700 ,  808  adaptive scheduler section 
           109 - 1  to  109 -N transmission buffer section 
           110 ,  200 ,  300 ,  400 ,  500 ,  810  transmission channel judgment section 
           201 ,  301 ,  401 ,  501  comparator 
           302 ,  402   502  selector 
           503  retransmission count control selector 
           601 ,  701  scheduler adopter 
           602 ,  702  high QoS packet preferential scheduler section 
           603  low QoS packet preferential scheduler section 
           703  sequential transmission packet preferential scheduler section 
           811  multiple transmission buffers