JP2010135909A - Radio communication apparatus, and radio communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To manage retransmission control of transmission data in multi-channel transmission with a simple structure. <P>SOLUTION: A radio communication apparatus is provided with a plurality of communication processing sections for performing communication by using different frequency channels and a flow control unit for sorting transmission frames into the plurality of communication processing sections. The respective communication processing sections have: transmission means for transmitting the sorted transmission frames; receiving means for receiving transmission confirmation frames from transmission destinations of the transmission frames; and retransmission control means for controlling retransmission of non-transmitted frames and notifying the flow control unit of the transmission situations of the sorted transmission frames. The flow control unit selects transmission frames from a buffer within a range of transmissible data amount and sorts them according to transmission situations of the respective communication processing sections into the transmission destination obtained according to frame size, the transmission situations of the transmission frames sorted into the communication processing sections, and reception buffer size of the transmission destination. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a technical field of wireless communication, and, for example, relates to a wireless communication apparatus and a wireless communication method that perform packet transmission using selective retransmission control in each of a plurality of frequency channels.

  In the IEEE802.11 wireless LAN standard where transmission using CSMA / CA (Carrier Sense Multiple Access with Collision Avoidance) is performed, the frequency band is expanded and the same destination is used using multiple frequency channels. On the other hand, a method for transmitting different data frames (hereinafter referred to as Multi-Channel transmission) has been studied.

  Conventionally, when a reception error is detected in Multi-Channel transmission, a retransmission control method has been studied in which a transmission side requests retransmission of data from the reception side to the transmission side, and a transmission side that receives the retransmission request retransmits data to the reception side. ing. (For example, see Patent Document 1)

  A data retransmission method in Multi-Channel transmission in Patent Document 1 will be described. First, the transmission side terminal has a data string (including data A and B) with a flag X1 indicating channel Ch1 and a data string (including data C and D) with a flag X2 indicating channel Ch2 respectively. Transmit simultaneously using Ch1 and channel Ch2. At the same time, the transmission side terminal manages transmission data for each channel (Ch). When the receiving side terminal detects an error in the data transmitted on the channel Ch2 due to error detection, the receiving side terminal discards the data string including the detected data and sends a retransmission request for the data string on the channel Ch2 to the transmitting side terminal. When receiving the retransmission request, the transmission side terminal recognizes the contents of the retransmission request and retransmits the data string transmitted on the channel Ch2 based on information managed for transmission data for each channel. As described above, Patent Document 1 discloses a system capable of retransmitting only a data string transmitted on a channel in which an error has occurred by managing transmission data for each channel and including a channel number in a retransmission request. ing.

Patent Document 2 proposes a method of performing data delivery confirmation on a channel basis and performing retransmission and releasing the transmission buffer memory based on a delivery confirmation signal in each channel.
JP 2002-281002 JP Japanese Patent Laid-Open No. 11-41281

  However, none of these are intended for automatic error retransmission (ARQ: Auto Repeat reQuest) control by a selective repeat method. For example, in Patent Document 1, when an error is detected only in data C in the data sequence transmitted on channel Ch2, only the channel number is notified at the time of retransmission request, so that data D in which no error is detected is also retransmitted in the data sequence Will do. Therefore, when the selective retransmission ARQ scheme is applied in the system of Patent Document 1, the receiving side terminal also notifies the sequence number of the data in which the error is detected at the time of retransmission request, so that the transmitting side terminal can detect the error detected data ( Only data C) can be retransmitted. However, when the selective retransmission ARQ method is used, it is possible to retransmit only erroneous data, so that the efficiency can be improved.On the other hand, the transmission data for each data unit (that is, every sequence number) is used for retransmission control. It is necessary to manage, and control is complicated in implementation.

  The system disclosed in Patent Document 2 is a configuration / system assuming that sequence numbers added to data to be transmitted are added independently in each frequency channel, and retransmission is also performed in the frequency channel. . Therefore, retransmission control and management of transmission data is performed independently for each frequency channel without being aware of the status of each other's frequency channel (without exchanging management information on each frequency channel). Therefore, even if Multi-Channel transmission is assumed, it will not be so complicated. However, in Multi-Channel transmission, the propagation path environment is generally different for each frequency channel, so when there is a retransmission request after transmission on a certain frequency channel, another frequency channel, which is a better propagation path environment, is sent. A method of transmitting after changing can be considered. When such a method is performed, it is not possible to perform transmission and retransmission for each frequency channel independently as in Patent Document 2, but management information on each frequency channel is exchanged, and each frequency channel is straddled. It is easy to imagine that the implementation becomes more complicated because it is necessary to manage the sequence numbers and the like collectively. In addition, when performing Multi-Channel transmission to the same receiving side terminal, simply adding an independent sequence number for each frequency channel simply controls the order of data received on different frequency channels at the receiving side terminal ( Re-Ordering control) is impossible.

  Also, in Multi-Channel transmission using CSMA / CA, it is considered that carrier sensing is performed independently in each frequency channel, and data transmission is performed in that frequency channel each time a transmission right is acquired. . Therefore, in general, the data transmission timing in each frequency channel is independent and not synchronized. Further, in the IEEE802.11 standard, due to carrier sense, it is necessary to send back a retransmission request signal (delivery confirmation signal) in a time called SIFS. From the above, in Multi-Channel transmission using CSMA / CA, the data transmission timing and retransmission request frame transmission timing in each frequency channel are synchronized as assumed in Patent Document 1 and Patent Document 2. In other words, the frequency channels are exchanged independently and in some cases in parallel. As described above, in a system in which retransmission request signals in respective frequency channels are returned at independent timings, it is expected that retransmission control / management of transmission data will be further complicated.

  The present invention has been made in consideration of the above points, and a wireless communication apparatus and a wireless communication method capable of realizing management of retransmission control of transmission data in multi-channel transmission with a simple configuration I will provide a.

A wireless communication device according to an aspect of the present invention includes:
A wireless communication device capable of transmitting a plurality of frames in parallel to the same destination using a plurality of frequency channels,
A sequence number adding unit for generating a plurality of transmission frames by adding a sequential number to each of the plurality of frames transmitted to the same destination;
A buffer for temporarily storing the transmission frame generated by the sequence number adding unit;
A plurality of communication processing units for performing communication using different frequency channels among the plurality of frequency channels;
A flow control unit that distributes transmission frames in the buffer to the plurality of communication processing units,
Each of the communication processing units
Storage means for storing a sequence number of the transmission frame distributed by the flow control unit;
Transmitting means for transmitting the transmission frame distributed by the flow control unit;
Receiving means for receiving a delivery confirmation frame representing a delivery status of the distributed transmission frame from a transmission destination of the transmission frame;
The delivery status of the assigned transmission frame is managed based on the delivery confirmation frame, retransmission control of an undelivered frame is performed among the assigned transmission frames, and the delivery status of the assigned transmission frame is indicated by the flow control unit. A retransmission control means for notifying to
The flow control unit determines the transmission destination from the frame size of the transmission frame distributed to each communication processing unit, the delivery status notified from each retransmission control unit, and the reception buffer size of the transmission destination acquired in advance. Calculate the amount of data that can be transmitted, select a transmission frame from the buffer within the range of the calculated data amount, and distribute the selected transmission frame to each of the communication processing units according to the delivery status of the transmission frame. It is characterized by.

A wireless communication device according to an aspect of the present invention includes:
A wireless communication device capable of transmitting a plurality of frames in parallel to the same destination using a plurality of frequency channels,
A sequence number adding unit for generating a plurality of transmission frames by adding a sequential number to each of the plurality of frames transmitted to the same destination;
A buffer for temporarily storing the transmission frame generated by the sequence number adding unit;
A plurality of communication processing units for performing communication using different frequency channels among the plurality of frequency channels;
A flow control unit that distributes transmission frames in the buffer to the plurality of communication processing units,
Each of the communication processing units
Storage means for storing a sequence number of the transmission frame distributed by the flow control unit;
Transmitting means for transmitting the distributed transmission frame;
Receiving means for receiving a delivery confirmation frame representing a delivery status of the distributed transmission frame from a transmission destination of the transmission frame;
The delivery status of the assigned transmission frame is managed based on the delivery confirmation frame, retransmission control of an undelivered frame is performed among the assigned transmission frames, and the delivery status of the assigned transmission frame is indicated by the flow control unit. A retransmission control means for notifying to
The flow control unit distributes the transmission frame in the buffer to each communication processing unit according to a delivery status of the transmission frame allocated to each communication processing unit.

A wireless communication method as one aspect of the present invention includes:
A wireless communication method capable of transmitting a plurality of frames to the same destination in parallel using a plurality of frequency channels,
A sequence numbering step for generating a plurality of transmission frames by adding a sequential number to each of the plurality of frames transmitted to the same destination;
A buffering step of temporarily storing the transmission frame generated by the sequence number adding unit in a buffer;
A distribution step of distributing transmission frames in the buffer to the plurality of frequency channels;
A storage step of storing each of the sequence numbers of the transmission frames assigned to the frequency channels;
For each frequency channel, a transmission step of transmitting the allocated transmission frame through the frequency channel;
A reception step of receiving, for each frequency channel, a delivery confirmation frame representing a delivery status of the distributed transmission frame from a transmission destination of the transmission frame;
A retransmission control step for managing the delivery status of the allocated transmission frame based on the delivery confirmation frame for each frequency channel, and performing retransmission control of undelivered frames among the allocated transmission frames;
The allocating step distributes the transmission frame in the buffer to each frequency channel according to a delivery status of the transmission frame in each frequency channel.

  According to the present invention, management of retransmission control of transmission data in multi-channel transmission can be realized with a simple configuration.

  Hereinafter, the present embodiment will be described in detail with reference to the drawings.

  FIG. 1 is a block diagram illustrating a configuration example of a wireless communication apparatus as an embodiment of the present invention.

  In the following, description will be made assuming that the system is based on the IEEE802.11 wireless LAN standard. However, the system is not necessarily based on the IEEE802.11 wireless LAN standard, and any system may be used. Although the description will be made assuming that four frequency channels are used for communication, any number of frequency channels may be actually used. In this case, only the number of processing units required for each frequency channel is changed.

  The wireless communication device of FIG. 1 includes four antenna units 31, four transmission / reception units 32, four MAC control units 33, one flow control unit 34, and a sequence number adding unit 35. The antenna unit 31, the transmission / reception unit 32, and the MAC control unit 33 are each configured to correspond to each frequency channel so that each of the frequency channels operates independently in four frequency channels. The circuit is often shared between the transmission / reception units of each other, and is not necessarily independent.

  Each antenna unit 31 transmits and receives a signal using a corresponding frequency channel.

  Each transmission / reception unit 32 performs data transmission / reception processing such as modulation processing and demodulation processing via the corresponding antenna unit 31.

  Each MAC (Media Access Control) control unit 33 performs MAC transmission / reception processing and retransmission control / management based on CSMA / CA in the frequency channel of the corresponding transmission / reception unit 32. The MAC control unit 33 includes a carrier sense unit 36 that performs carrier sense processing and a retransmission control unit 37 that performs retransmission control processing. The retransmission control unit 37 includes a bitmap extraction unit 38 that extracts bitmap information from a delivery confirmation frame (Block Ack frame) addressed to the own station received by the transmission / reception unit 32. A set of the MAC control unit 33 and the transmission / reception unit 32 corresponds to, for example, a communication processing unit of the present invention.

  The sequence number adding unit 35 receives data (frame) requested to be transmitted from an upper layer and adds a sequence number. Data (frame) to which a sequence number is added is referred to as transmission data (transmission frame). The sequence number is added so as to be sequentially incremented by 1 in the order received from the upper layer.

  The flow control unit 34 performs transmission flow control of transmission data without depending on each frequency channel. The flow control unit 34 receives the data (transmission data) with the sequence number added from the sequence number adding unit 35, and distributes the data to each MAC control unit 33 according to which frequency channel is used to transmit the transmission data 39. The MAC control unit 33 is provided independently for the number of frequency channels on which transmission / reception is performed, but only one flow control unit 34 is provided regardless of the number of frequency channels on which transmission / reception is performed.

  FIG. 2 is a flowchart showing a flow of data transmission processing and retransmission processing performed in the wireless communication apparatus of FIG.

  First, a data transmission request occurs in the upper layer (S101), and the data requested to be transmitted is sent to the sequence number adding unit 35, and a sequence number is added (S102).

  The sequence number adding unit 35 manages a sequence number for each data transmission destination, and adds a sequence number incremented in the order of data generation for each same destination.

  The data (transmission data) to which the sequence number is added is input to the flow control unit 34 and stored in a storage buffer that temporarily stores the transmission data. Here, the storage buffer is arranged in the flow control unit 34, but may be arranged outside the flow control unit 34. The data distribution unit 39 in the flow control unit 34 determines transmission data to be transmitted and a frequency channel to be transmitted, and distributes the transmission data to the MAC control unit 33 of the determined frequency channel (S103, S104).

  More specifically, in the flow control unit 34, for each transmission destination, the reception buffer size of the transmission destination acquired in advance, the data size of the transmission data allocated to the MAC control unit 33 of each frequency channel, and the transmission of the transmission data Based on the confirmation status, the amount of transmission data is determined so as not to overflow the receiving buffer at the transmission destination (S103).

  At this time, the flow control unit 34 uses the smallest sequence number among the entire transmission data sequence numbers assigned to each MAC control unit 33 as a reference, and the smallest sequence number (Unrecieved Starting Sequence Number) that has not been acknowledged. : USSN) is grasped and managed, and the amount of transmission data is determined using this USSN. The reception buffer size of the transmission destination is acquired by exchanging a prior management frame with the transmission destination. The flow control unit 34 holds the data size of the transmission data distributed to each MAC control unit 33 in order to determine the transmission data amount. The data size of the transmission data that has been confirmed to be delivered may be deleted.

  The flow control unit 34 selects transmission data from the storage buffer in ascending order of the sequence number within the determined transmission data amount range, and distributes it to the MAC control unit 33 of each frequency channel according to the respective delivery confirmation status (S104 ). An example of the distribution is shown in FIG. In the example of FIG. 3, a plurality of transmission data having sequence numbers (SN) 1 to 4, 5 to 8, 9 to 12, and 13 to 15 are allocated to the respective frequency channels. Each distributed transmission data is stored in the transmission buffer until transmission is completed. At that time, the transmission buffer may be provided in the MAC control unit 33 of each frequency channel, may be provided in the flow control unit 34, or separately from the MAC control unit 33 and the flow control unit 34. It may be provided where it can be accessed from each. When it is provided in the flow control unit 34, it can also serve as the above-described storage buffer for temporarily storing. Only the information exchanged between the blocks in each process differs depending on where the transmission buffer is provided. Note that the flow control unit 34 does not need to retain information indicating which sequence number of transmission data is allocated to which frequency channel.

  Each MAC control unit 33 to which transmission data is distributed from the flow control unit 34, that is, a data transmission request is made, holds the sequence number (SN) of the distributed transmission data in the sequence number storage means (S105), and the carrier Using the sense unit 36, transmission right acquisition processing by CSMA / CA in each frequency channel is performed independently (S106).

  The MAC control unit 33 in each frequency channel outputs the transmission data to each transmission / reception unit 32 at the timing when the transmission right is acquired, and the transmission / reception unit 32 performs modulation processing, D / A conversion, etc. necessary for transmission. Then, data transmission is performed to the transmission partner terminal via the antenna unit 31 (S107).

  Here, the retransmission control unit 37 in the MAC control unit 33 holding the sequence number in step S106 manages the delivery status (transmission state) for each sequence number as well as holding the sequence number.

  In the example of FIG. 3, the retransmission control unit 37 of the frequency channel Ch_1 holds values of SN = 1 to 4 and manages the transmission state. Here, it is not necessary to hold information such as how transmission data is distributed to other frequency channels, and the retransmission control unit 37 of each frequency channel transmits the transmissions distributed to itself from the flow control unit 34. Only holds the sequence number of the data.

  At this time, each retransmission control unit 37 flushes the sequence number information in the sequence number storage unit each time transmission data is distributed from the flow control unit 34, and holds the new sequence number in the sequence number storage unit. To do. That is, the sequence number holding timing in the retransmission control unit 37 is set only at the time of distribution from the flow control unit 34 (at the time of data transmission request), and is not required to be held at other timings. When a new data distribution is input, the sequence number information and the transmission state that have been held so far are discarded once, and only the sequence number by the new data distribution is held. In this way, implementation complexity can be reduced.

  In this way, instead of adding an independent sequence number to each frequency channel, by distributing the data to which the sequence number is added to each frequency channel, the receiving terminal that is the transmission destination receives each frequency channel. The order control (Re-Ordering control) of the data received in the above becomes possible. That is, by checking the sequence number of the data received in each frequency channel on the receiving terminal side, it becomes possible to grasp the sequence number sequence of the received data between the respective frequency channels. Note that the sequence number adding method in the sequence number adding unit 35 adds a sequence number so that the order of data received over a plurality of frequency channels can be controlled with the receiving terminal side as described above. Anything can be used.

  Subsequently, a flow at the time of retransmission for each transmission data independently transmitted using each frequency channel by the above flow will be described. As shown in FIG. 3, after transmitting data on each frequency channel, a delivery confirmation frame for selective retransmission is returned for transmission data transmitted on each frequency channel after SIFS (= 16 us) time has elapsed from the receiving terminal side. In the IEEE802.11 wireless LAN system, a delivery confirmation frame for selective retransmission is returned in a format called a Block Ack frame shown in FIG. 4 (S108).

  In the Block Ack frame, since the frame length is fixed, the reception success / failure result (delivery status) of each received sequence number is notified using a fixed-length bitmap (Bitmap) as shown in Fig. 4. ing. Each bit (Bit) in the Bitmap corresponds to each sequence number based on the sequence number indicated in the Starting Sequence Number Control (SSN) field. By referring to each Bit, the frame of each sequence number The delivery status can be grasped. That is, the transmitting terminal can grasp which sequence number frame is correctly received and which sequence number frame has an error. The transmitting side terminal retransmits the frame having the sequence number having an error.

  FIG. 5 shows an example of the SSN field and Bitmap field in the Block Ack frame.

  Transmission data with sequence number (SN) = 1, 2, 3, 4 is transmitted, and transmission data with SN = 1, 2, 4 is correctly received at the receiving terminal, and transmission data with SN = 3 cannot be received correctly An example of the case is shown. As a matter of course, since the transmission data after SN = 5 has not been received on the receiving side, all the fields corresponding to SN = 5 and after are set to 0 and a reply is made.

  In the wireless communication apparatus according to the present embodiment, each antenna unit 31 receives a Block Ack frame returned from each frequency channel at each timing, and each of the transmission / reception units 32 performs processing such as demodulation. Thereafter, the data is input to the retransmission control unit 37 of each MAC control unit 33. In the retransmission control unit 37, the Bitmap extraction unit 38 extracts the Bitmap of the received Block Ack frame (S109). The retransmission control unit 37 compares the extracted bitmap with the sequence number stored when the data is distributed from the flow control unit 34, updates the transmission state, and transmits the unacknowledged transmission data. Is retransmitted as a retransmission frame (S110).

  For example, in Ch_1 of FIG. 3, when the result of Bitmap is the example of FIG. 5, an error has occurred in the transmission data of sequence number SN = 3 from the comparison between the sequence number held by itself and Bitmap. Figure out things. Then, the transmission state for each held sequence number is updated. Specifically, for SN = 1, 2, and 4, it is updated as “ACK response completed data”, and for SN = 3, “ACK unacknowledged data” is maintained and SN = 3 transmission data is updated. As a retransmission frame, retransmission is performed again via the transmission / reception unit 32 and the antenna unit 31. In this manner, the transmission state for the sequence number held in each retransmission control unit 37 is updated every time a Block Ack frame returned by the frequency channel is received.

  Here, the MAC controller 33 of each frequency channel ignores Bitmap information not included in the held sequence number as don't care. For example, in the case of Ch_1 in FIG. 3, 0 is returned after SN = 5, but it can be understood from the stored sequence number that the transmission data transmitted by itself on the frequency channel is up to SN = 4. The transmission state after = 5 is ignored as don't care. That is, even if the bit corresponding to SN = 5 or later in the Bitmap is 0, the retransmission control unit 37 in the frequency channel does not handle SN = 5 or later as data to be retransmitted.

  Even in the conventional retransmission control that does not assume Multi-Channel transmission, the transmission state is managed with only two values of “ACK response completed data” and “ACK non-response data” for each transmitted data. Also, data that was not transmitted was treated as don't care even if it was 0 in Bitmap. However, in Multi-Channel transmission, as shown in the example of FIG. 3, data transmission of SN = 5 to 8 is already performed in Ch_2 at the timing of receiving the delivery confirmation signal (Block Ack frame) in Ch_1. Therefore, in conventional retransmission control management that does not assume Multi-Channel transmission, when the Block Ack frame in Ch_1 is received, the data of SN = 5 to 8 is already transmitted data. It is not subject to 't care. That is, since the ACK response is not obtained for the data of SN = 5 to 8, the transmission state is managed as the state of “ACK unacknowledged data”. Therefore, even if the bit corresponding to the data after SN = 5 in the Bitmap in the Block Ack frame at Ch_1 is 0, it will be recognized that an error has occurred in these data, and SN = 5 or later Data may also be retransmitted. Since data after SN = 5 is acknowledged with an ACK response in the subsequent Block Ack frame in Ch_2, it is inherent that the data retransmission after SN = 5 will be performed when the Block Ack frame is received in Ch_1. Since retransmission is unnecessary at the timing, it causes a deterioration in throughput.

  In this regard, the embodiment of the present invention is configured so as not to cause such a retransmission problem in Multi-Channel transmission that can be transmitted at different arbitrary timings in each frequency channel. Compared to a case where frequency channels are managed and controlled collectively, each MAC control unit 33 and flow control unit 34 separates and manages each processing content. That is, the retransmission control unit 37 in the MAC control unit 33 manages and controls only the data transmitted on its own frequency channel without having to be aware of the transmission status on other frequency channels. In this way, it is possible to realize an apparatus that can prevent unnecessary retransmission without complicating the implementation.

  The retransmission processing of transmission data in each frequency channel is as follows: (1) All transmission data distributed from the flow control unit 34 is in the “ACK response completed” state, that is, transmission of all transmission data is completed ( S111 (YES), (2), or until the transmission data allowable delay time (Tx Lifetime) is reached (S112 YES) (3) or until the number of retransmissions reaches the threshold (S113 YES) (S116) .

  The threshold for the number of retransmissions in (3) above may be the Retry Limit value (maximum number of retransmissions) specified in the IEEE802.11 standard, or may be set to a value smaller than the Retry Limit value. For example, when it is not assumed that retransmission is performed by switching to another frequency channel, it is not necessary to set a value smaller than the Retry Limit value. In other words, by setting a value smaller than the Retry Limit value, it is possible to perform retransmission by switching to another frequency channel up to the Retry Limit value.

  When each of the above conditions (1) to (3) is satisfied, each MAC control unit 33 stops transmission (retransmission) processing on the frequency channel, releases each transmission buffer (S114), and performs flow control. Notification to the unit 34 is performed (S117). Until that time (from the time when data is distributed from the flow control unit 34 until one of the above conditions is reached), the MAC control unit 33 is separated from the flow control unit 34 for processing.

  That is, the data distribution in the flow control unit 34 is performed once the data is distributed to the MAC control unit 33 of each frequency channel, and then until the above-mentioned notification from each MAC control unit 33 is performed. The following data distribution is not performed for the control unit 33. As a result, the processing in each MAC control unit 33 and the processing in the flow control unit 34 can be separated. In the flow control unit 34, delivery in each frequency channel is notified until there is a notification from each MAC control unit 33. It is not necessary to grasp the success / failure status or the retransmission status. In addition, the MAC control unit 33 starts processing when there is data distribution from the flow control unit 34, and regarding the subsequent retransmission control, the flow control unit 34 does not grasp any situation in other frequency channels. Therefore, it is possible to grasp and manage only the sequence number of transmission data transmitted on its own frequency channel and perform retransmission control. In this way, complicated retransmission control can be avoided. Also, as described in step S105, the transmission data sequence number is held in the MAC control unit 33 every time transmission data is distributed from the flow control unit 34, the sequence number information so far in the sequence number storage means is stored. Flush (erase) and keep only the new sequence number, but the next data distribution from the flow control unit 34 will not be performed until a notification is sent from the MAC control unit 33 according to any of the above conditions Therefore, even if such a configuration is used, no particular problem occurs.

  Next, details of the notification process (S117) from the MAC control unit 33 to the flow control unit 34 and subsequent processes will be described. The details of the notification processing and the processing after notification vary depending on the satisfied conditions.

  First, in the case of notification that transmission of all transmission data has been completed (YES in S111), at least that fact and the value of the largest sequence number held (that is, the largest sequence number for which transmission completion has been confirmed) Value) and the value of the smallest sequence number (that is, the value of the smallest sequence number for which transmission completion was confirmed) are notified to the flow control unit 34. For example, in the case of Ch_1 in FIG. 3, the largest sequence number value corresponds to SN = 4, and the smallest sequence number value corresponds to SN = 1.

  As a result, the flow control unit 34 notified of these values and the value of the notified smallest sequence number and the USSN held by the flow control unit 34 (of the entire sequence number of transmission data distributed to each MAC control unit 33) The smallest sequence number that has not been confirmed for delivery) is compared. As a result of the comparison, when the USSN held by the flow control unit 34 matches the value of the smallest sequence number notified from the MAC control unit 33, the flow control unit 34 sets the USSN value held by the flow control unit 34 The value is updated to “the largest sequence number +1 notified from the MAC control unit 33” (S118). By receiving this notification, the flow control unit 34 can grasp that the delivery confirmation has been performed up to the transmission data of the largest sequence number that has been notified continuously from the USSN held so far.

  This is because the receiving terminal side controls the order of received data (Re-Ordering control). It is released from the reception buffer and transferred to the upper layer. Therefore, the flow control unit 34 updates the USSN held in accordance therewith, and the updated USSN determines the amount of transmission data within a range in which no overflow of the reception buffer occurs during subsequent data transmission to the receiving terminal. Can be used. For example, the transmission data up to the maximum sequence number among the USSNs assigned to each MAC control unit 33 has not yet reached, that is, the buffering is performed for the ordering control (Re-Ordering control) in the receiving buffer of the receiving terminal. Assuming that the amount of data that can be newly transmitted can be determined based on the reception buffer size of the transmission destination.

  When the value of the USSN held by the flow control unit 34 does not match the value of the smallest sequence number notified from the MAC control unit 33, the MAC control unit 33 in the other frequency channel determines the sequence between them. Recognizing that the transmission data of the number is being transmitted, the USSN is not updated, and the notified smallest sequence number and the notified largest sequence number are stored internally. Then, when the USSN is updated later in connection with another frequency channel, the updated USSN is compared with the stored smallest sequence number. Update to +1 value.

  After the USSN is updated as necessary in step S118, the process returns to the determination of the data amount and the distribution of the transmission data (S103, S104). For example, the flow control unit 34 determines the amount of data as described above, selects and extracts transmission data from the storage buffer so as to be within the determined amount of data, and extracts the extracted transmission data from the MAC control that performed the above notification. Distribute to part 33.

In the above, at the time of notification to the flow control unit 34, at least that fact and the value of the largest sequence number and the value of the smallest sequence number held are notified. However, it is also possible to update the USSN without notifying the sequence number from the MAC control unit 33 by configuring the flow control unit 34 to hold which sequence number transmission data is allocated at the time of data distribution. is there. (This also applies to other conditions (2) or (3))
Further, since any transmission data has been confirmed for delivery and transmission has been completed, the MAC control unit 33 also releases the buffer memory for all the transmission data stored in the transmission buffer (S114). However, the transmission buffer may be released before or after the notification to the flow control unit 34 (the flow in FIG. 2 shows an example of the former case). Further, the buffer memory may be released not by the MAC control unit 33 but by the flow control unit 34.

  Next, a notification that the allowable delay time (transmission timeout) of the transmission data has been reached (YES in S112), or the number of retransmissions is a threshold value (here, the Retry Limit value defined in the IEEE802.11 standard (the maximum number of retransmissions) )), The flow control unit 34 is notified of at least the value of the largest sequence number and the smallest sequence number held therein (YES in S113).

  In this case, some of the distributed transmission data has not been acknowledged (that is, “ACK response completed data” and “ACK non-response data” are mixed), but “ACK non-response data” The transmission data corresponding to the above is handled in the same way as the transmission data whose delivery has been confirmed as data that does not need to be transmitted any more (insignificant) due to Retry Out or transmission timeout. In this case, the transmission data can be retransmitted as necessary by the upper layer.

  Thus, the flow control unit 34 notified of these compares the notified value of the smallest sequence number with the sequence number (USSN) held by itself. As a result of the comparison, when the USSN held by the flow control unit 34 matches the value of the smallest sequence number notified from the MAC control unit 33, the flow control unit 34 sets the USSN value held by the flow control unit 34 Update to the value of the largest sequence number +1 notified from the MAC control unit 33 (S118). After step S118, the process returns to the determination of the data amount and the transmission data distribution process (S103, S104).

  When the value of the USSN held by the flow control unit 34 does not match the value of the smallest sequence number notified from the MAC control unit 33, the MAC control unit 33 in the other frequency channel determines the sequence between them. The transmission data of the number is recognized as being transmitted, the USSN is not updated, and the notified smallest sequence number and the notified largest sequence number are stored internally. Then, when the USSN is updated later in connection with another frequency channel, the updated USSN is compared with the stored smallest sequence number. Update to +1 value.

  In addition, since any transmission data is either data for which delivery confirmation has been obtained or data to be discarded because there is no need to transmit any more, the MAC control unit 33, those stored in the transmission buffer The buffer memory for all transmission data is also released (S114). However, the release of the transmission buffer may be performed before or after the notification to the flow control unit 34 (the flow in FIG. 2 shows an example of the former case). Further, the buffer memory may be released not by the MAC control unit 33 but by the flow control unit 34.

  Next, in the case of notification that the number of retransmissions has reached a threshold (here, a threshold smaller than the Retry Limit value) (YES in S113), at least that fact, the value of the smallest sequence number held, and the delivery confirmation The flow control unit 34 is notified of the value of the sequence number of transmission data that has not been removed (transmission data whose transmission state is “ACK unacknowledged data”) (S117).

  The flow control unit 34 notified of them compares the notified value of the smallest sequence number with the sequence number (USSN) held by itself. As a result of the comparison, when the USSN held by the flow control unit 34 matches the value of the smallest sequence number notified from the MAC control unit 33, the flow control unit 34 sets the USSN value held by the flow control unit 34 Update to the value of the smallest sequence number among the transmission data notified from the MAC control unit 33 and for which delivery confirmation has not been obtained (S118).

  For example, the sequence number held in the MAC control unit 33 is SN = 1 to 5, and each transmission state is “ACK responded data”, “ACK responded data”, “ACK not responded” sequentially from SN = 1 In the case of “data”, “ACK response completed data”, and “ACK non-response data”, the sequence number value to be notified as the sequence number value of the transmission data for which delivery confirmation has not been obtained is SN = 3,5. The sequence number to be notified as the value of the smallest sequence number held is SN = 1. In the flow control unit 34, when the sequence number USSN is 1, the USSN is updated to 3. (That is, update to USSN = 3 as data that has been confirmed to be delivered without missing until SN = 2. If the value of the smallest sequence number that has been notified does not match the USSN at the stage of comparison. Recognizes that the sequence number data between them is being transmitted (retransmitted) by the MAC control unit 33 in another frequency channel, and does not update the USSN. When it is done, the comparison is performed again, and if it matches, the update is performed.)

  Further, the flow control unit 34 has not yet reached the Retry Limit value for the notified transmission data (SN = 3, 5 in the above example) for which the delivery confirmation has not been obtained. After setting the retry bit, considering the propagation path environment in each frequency channel including the frequency channel originally transmitting, the data is again transmitted to the MAC control unit 33 of any frequency channel. Distribution is performed and retransmission is performed (S103, S104). At the time of data distribution for retransmission, the current number of retransmissions is notified to the MAC control unit 33 that distributes transmission data.

  Further, since transmission has been completed only for transmission data for which delivery confirmation has been obtained, the MAC control unit 33 also releases those buffer memories stored in the transmission buffer (S114). The release of the transmission buffer may be performed before or after the notification to the flow control unit 34 (the flow in FIG. 2 shows an example of the former case). Further, the buffer memory may be released not by the MAC control unit 33 but by the flow control unit 34.

  In addition to satisfying any of the above conditions (1), (2) or (3) (YES in S111, YES in S112, YES in S113), the following conditions are satisfied (YES in S115) Notification may also be performed. By making this notification, the USSN held in the flow control unit 34 can be updated at an earlier timing. This will be described in detail below.

  When the Block Ack frame is received, the MAC control unit 33 changes the value of the smallest sequence number among the transmission data that has not been acknowledged (transmission data whose transmission state is “ACK unacknowledged data”). When it becomes larger (YES in S115), the flow controller 34 is notified (S119). The information notified to the flow control unit 34 and the processing of the flow control unit 34 after the notification are the same as in the case of notification when the number of retransmissions reaches a threshold value smaller than the Retry Limit value.

  That is, the MAC controller 33 holds the value of the smallest sequence number held and the value of the sequence number of transmission data for which delivery confirmation has not been confirmed (transmission data whose transmission state is “ACK unacknowledged data”). Notify the flow control unit 34. The flow control unit 34 compares the held USSN with the value of the smallest sequence number that has been notified from the MAC control unit 33 and has not been confirmed for delivery, and if these match, the flow control unit 34 updates the held USSN value to the value of the smallest sequence number that has been notified from the MAC control unit 33 and has not been acknowledged (S120). In this way, the update timing of the retained information in the flow control unit 34 can be implemented at an earlier timing, and more accurate determination can be made each time when determining the amount of data to be transmitted.

  However, in the case of this notification (the notification in S119), the flow control unit 34 does not perform the next data distribution to the MAC control unit 33 at the time of notification from the MAC control unit 33. In other words, this notification is merely a notification for enabling the update of the sequence number USSN held in the flow control unit 34 to be performed at an earlier timing. Until the condition for performing any of the notifications (S117 notification) is satisfied (until either S111 YES, S112 YES, or S113 YES), retransmission control is continued on the frequency channel. (S116). Also, the flow control unit 34 does not perform the next data distribution to the MAC control unit 33 until receiving any notification (notification S117) other than the present notification (notification S119).

  As described above, the embodiment of the present invention includes the MAC control unit 33 for each frequency channel and the flow control unit 34 that is always one without depending on the number of frequency channels. And only the information necessary for each control is held and updated at the timing of each control unit. By doing this, when performing retransmission control by selective retransmission ARQ in Multi-Channel transmission, awareness of the transmission status on each other's frequency channel regarding the management of retransmission control of transmission data and transmission buffer memory release etc. And can be controlled independently.

  In other words, the flow control unit 34 does not need to grasp the retransmission status in each frequency channel each time, and does not require management across each frequency channel, and the retained information is triggered by the notification from each retransmission control unit. Since it only needs to be updated, the control (management) in the flow control unit becomes easy (from the flow control unit, the retransmission control unit in each frequency channel is independent until notified from the retransmission control unit. Appears to continue resending). In addition, each retransmission control unit can independently perform retransmission control without exchanging the situation in each frequency channel, and even if the frame transmission timing in each frequency channel is different, it is easy. realizable. With this configuration, when the frame is allocated in the retransmission control unit of each frequency channel, there is no problem even if the previous retained information can be discarded, and the sequence number divided every time is retained. be able to. Thus, even when the frequency channel is changed at the time of retransmission, processing can be realized without complication.

  Further, in the embodiment of the present invention, even when Multi-Channel transmission is performed by the flow control unit 34, the transmission partner can prevent reception buffer overflow from occurring by performing transmission in consideration of the reception buffer status of the transmission partner.

  Further, in the embodiment of the present invention, sequence numbers are added in consideration of the order control (Re-Ordering control) of received frames in each frequency channel on the receiving terminal side in Multi-Channel transmission, Even when transmission on each frequency channel is transmitted at an independent timing by CSMA / CA, the receiving terminal can rearrange the sequence numbers by order control and transfer the received frame to the upper layer. .

  Furthermore, in the embodiment of the present invention, when determining the retransmission frame using the Bitmap information in the delivery confirmation frame, at least the information on the sequence number of the frame that is not transmitted on the corresponding frequency channel is ignored. In Multi-Channel transmission, it is possible to prevent unnecessary retransmission that may occur when transmission is performed at different timings in each frequency channel.

  Note that the present invention is not limited to the above-described embodiment as it is, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. In addition, various inventions can be formed by appropriately combining a plurality of components disclosed in the embodiment. For example, some components may be deleted from all the components shown in the embodiment. Furthermore, constituent elements over different embodiments may be appropriately combined.

1 is a block diagram showing a configuration example of a wireless communication apparatus as an embodiment of the present invention. FIG. 3 is a flowchart showing a processing flow in the wireless communication apparatus of FIG. 2. The figure explaining an example of Multi-Channel transmission using CSMA / CA. The figure which shows the delivery confirmation frame (Block Ack frame) format in IEEE802.11 specification. The figure which shows the example of Bitmap of a Block Ack frame.

Explanation of symbols

31: Antenna 32: Transmission / reception unit 33: MAC control unit 34: Flow control unit 35: Data distribution unit 36: Carrier sense unit 37: Retransmission control unit 38: Bitmap extraction unit 39: Data distribution unit

Claims (11)

A wireless communication device capable of transmitting a plurality of frames in parallel to the same destination using a plurality of frequency channels,
A sequence number adding unit for generating a plurality of transmission frames by adding a sequential number to each of the plurality of frames transmitted to the same destination;
A buffer for temporarily storing the transmission frame generated by the sequence number adding unit;
A plurality of communication processing units for performing communication using different frequency channels among the plurality of frequency channels;
A flow control unit that distributes transmission frames in the buffer to the plurality of communication processing units,
Each of the communication processing units
Storage means for storing a sequence number of the transmission frame distributed by the flow control unit;
Transmitting means for transmitting the transmission frame distributed by the flow control unit;
Receiving means for receiving a delivery confirmation frame representing a delivery status of the distributed transmission frame from a transmission destination of the transmission frame;
The delivery status of the assigned transmission frame is managed based on the delivery confirmation frame, retransmission control of an undelivered frame is performed among the assigned transmission frames, and the delivery status of the assigned transmission frame is indicated by the flow control unit. A retransmission control means for notifying to
The flow control unit determines the transmission destination from the frame size of the transmission frame distributed to each communication processing unit, the delivery status notified from each retransmission control unit, and the reception buffer size of the transmission destination acquired in advance. Calculate the amount of data that can be transmitted, select a transmission frame from the buffer within the range of the calculated data amount, and distribute the selected transmission frame to each of the communication processing units according to the delivery status of the transmission frame. A wireless communication device. The retransmission control means in each communication processing unit notifies the delivery status when the delivery status for all the transmission frames distributed from the flow control unit is confirmed to be delivered,
The wireless communication apparatus according to claim 1. The retransmission control means in each communication processing unit is configured such that the number of continuous retransmissions of at least one transmission frame is a predetermined threshold before the delivery status of all the transmission frames distributed from the flow control unit is confirmed to be delivered. The wireless communication apparatus according to claim 2, wherein the notification of the delivery status is made when the value reaches. The retransmission control means in each of the communication processing units, when a predetermined transmission allowable delay time has elapsed before the delivery status of all the transmission frames distributed from the flow control unit is confirmed to be delivered, The wireless communication apparatus according to claim 2, wherein notification of a situation is performed. The retransmission control means in each communication processing unit notifies the delivery status every time the delivery status of the frame with the smallest sequence number among the transmission frames in which the delivery status has not reached has been confirmed. The wireless communication apparatus according to claim 1. The flow control unit performs the calculation of the data amount, selection and distribution of the transmission frame when receiving the notification of the delivery status from at least one of the retransmission control units, and distributes the transmission frame The wireless communication apparatus according to any one of claims 1 to 5, wherein the wireless communication apparatus is not performed before receiving notification of the delivery status from at least one of the reproduction control means. The flow control unit manages the smallest sequence number USSN that has not been acknowledged among the transmission frames distributed to each communication processing unit based on the delivery status notified from each retransmission control unit, and the sequence number USSN The amount of data that can be transmitted to the transmission destination is calculated from the reception buffer size of the transmission destination acquired in advance. The wireless communication apparatus according to any one of claims 1 to 6. Each of the communication processing units
When the transmission frame is allocated from the flow control unit, the sequence number of the transmission frame allocated before is deleted from the storage means,
The wireless communication apparatus according to any one of claims 1 to 7, wherein information on a delivery status of the transmission frame allocated before is deleted. A wireless communication device capable of transmitting a plurality of frames in parallel to the same destination using a plurality of frequency channels,
A sequence number adding unit for generating a plurality of transmission frames by adding a sequential number to each of the plurality of frames transmitted to the same destination;
A buffer for temporarily storing the transmission frame generated by the sequence number adding unit;
A plurality of communication processing units for performing communication using different frequency channels among the plurality of frequency channels;
A flow control unit that distributes transmission frames in the buffer to the plurality of communication processing units,
Each of the communication processing units
Storage means for storing a sequence number of the transmission frame distributed by the flow control unit;
Transmitting means for transmitting the transmission frame distributed by the flow control unit;
Receiving means for receiving a delivery confirmation frame representing a delivery status of the distributed transmission frame from a transmission destination of the transmission frame;
The delivery status of the assigned transmission frame is managed based on the delivery confirmation frame, retransmission control of an undelivered frame is performed among the assigned transmission frames, and the delivery status of the assigned transmission frame is indicated by the flow control unit. A retransmission control means for notifying to
The said flow control part distributes the said transmission frame in the said buffer to each said communication processing part according to the delivery condition of the said transmission frame allocated to each said communication processing part. The radio | wireless communication apparatus characterized by the above-mentioned. The delivery confirmation frame includes bitmap information in which a sequence number is associated with a bit indicating the presence or absence of delivery,
The wireless communication apparatus according to claim 9, wherein the retransmission control unit ignores information of a sequence number different from a sequence number of the distributed transmission frame in the bitmap information. A wireless communication method capable of transmitting a plurality of frames to the same destination in parallel using a plurality of frequency channels,
A sequence numbering step for generating a plurality of transmission frames by adding a sequential number to each of the plurality of frames transmitted to the same destination;
A buffering step of temporarily storing the transmission frame generated by the sequence number adding unit in a buffer;
A distribution step of distributing the transmission frame in the buffer to the plurality of frequency channels;
A storage step of storing each of the sequence numbers of the transmission frames assigned to the frequency channels;
For each frequency channel, a transmission step of transmitting the allocated transmission frame through the frequency channel;
A reception step of receiving a delivery confirmation frame representing a delivery status of the distributed transmission frame for each frequency channel from a transmission destination of the transmission frame;
A retransmission control step for managing the delivery status of the allocated transmission frame based on the delivery confirmation frame for each frequency channel, and performing retransmission control of an undelivered frame among the allocated transmission frames;
In the wireless communication method, the allocating step distributes the transmission frame in the buffer to each frequency channel according to a delivery status of the transmission frame in each frequency channel.

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