JP2009141527A - Communication apparatus and communication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To suppress the deterioration of a throughput due to environmental variation while maintaining interconnectivity with the existing device. <P>SOLUTION: A first communication apparatus aggregates and transmits a plurality of pieces of transmission data to a first frame to be transmitted to a second communication apparatus. The first communication apparatus reduces the number of pieces of transmission data to be aggregated in the first frame without reducing the transmission rate of the first frame according to a retransmission success state when a receiving state in the second communication apparatus is smaller than a predetermined value P. Alternatively, the first communication apparatus reduces the transmission rate without reducing the number of pieces of data to be aggregated in the first frame. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates generally to communication devices, and more particularly to communication devices that use frame aggregation.

  According to IEEE 802.11n, which is currently being developed, frame aggregation will be adopted. Frame aggregation is a data transfer method in which a plurality of frames are aggregated and transferred into one frame. If frame aggregation is adopted, the MAC header can be reduced to one, so that transmission efficiency is improved.

  In a wireless LAN system that uses frame aggregation, the frame length becomes longer than when frame aggregation is not used. However, when the frame length is long, there is a problem that the throughput is remarkably lowered due to burst noise and intense channel fluctuation over a long period of time.

In order to solve this problem, according to Patent Document 1, the length of the data portion of the transmission frame is shortened if the fluctuation of the propagation path is severe, and the length of the data portion of the transmission frame is lengthened if the fluctuation is moderate. An invention has been proposed.
JP 2006-173867 A

  However, as in Patent Document 1, if a special protocol that does not exist in the standard is used in order to prevent a decrease in throughput due to frame aggregation, a problem arises in interconnectability.

  A problem also arises when space-time block coding (STBC) of IEEE 802.11n (draft 2.0) is used by only one terminal for transmission and the other terminal does not use STBC for transmission. In this case, the received signal level at the other terminal which is the other terminal is improved, but the received signal level of the data received from the other terminal is not improved. That is, for one terminal, data of the local station is easily received, but data from the other terminal remains difficult to receive.

  In such a situation, it is not possible to identify whether a reception failure has occurred because the frame has not arrived or whether a reception failure has occurred because the Ack for the frame has not returned. Such a difference in cause affects whether or not the aggregation length should be changed, so it is important to identify the cause. For example, since the former has a problem in the propagation state of the forward link, it is necessary to change the aggregation length. However, since the latter only has a problem in the propagation situation of the reverse link, it is not always necessary to change the aggregation length.

  Therefore, an object of the present invention is to solve at least one of such problems and other problems. For example, an object of the present invention is to propose an aggregation length determination algorithm that can suppress a decrease in throughput due to environmental changes while maintaining interoperability with existing devices. Other issues can be understood throughout the specification.

  In the present invention, for example, a first communication device that aggregates and transmits a plurality of transmission data in a first frame to be transmitted to a second communication device may perform retransmission when the reception status in the second communication device is smaller than a predetermined value P. Depending on the success situation, the number of transmission data aggregated in the first frame is reduced without decreasing the transmission rate of the first frame, and the number of transmission data aggregated in the first frame is decreased. Reduce the transmission rate.

  According to the present invention, the aggregation length can be determined while suppressing a decrease in throughput due to environmental changes.

  An embodiment of the present invention is shown below. The individual embodiments described below will help to understand various concepts, such as the superordinate concept, intermediate concept and subordinate concept of the present invention. Further, the technical scope of the present invention is determined by the scope of the claims, and is not limited by the following individual embodiments.

  FIG. 1 is a diagram illustrating an example of a communication system including a plurality of wireless communication devices according to the embodiment. The communication system includes wireless LAN devices (STA102, STA103) that are examples of the first communication device and the second communication device. Here, as an example, it is assumed that the network 101 is compliant with IEEE 802.11n (draft 2.0). Needless to say, the present invention can be applied to other standards. The STA 102 and the STA 103 establish a network 101 and communicate with each other. Note that three or more wireless LAN devices may participate in the network 101.

  FIG. 2 is an exemplary block diagram of the wireless LAN device according to the embodiment. The CPU 200 is connected to the memory 201 and the IF unit 202. The IF unit 202 is connected to the wireless unit 203. The frame generated by the CPU 200 is transmitted to the counterpart device through the IF unit 202 and the wireless unit 203. The wireless unit 203 receives a frame transmitted by the counterpart device. The received frame is passed to the CPU 200 through the IF unit 202.

  FIG. 3 is an exemplary block diagram illustrating functions included in the wireless LAN device according to the embodiment. Here, it is assumed that each unit is realized by various hardware (mainly CPU 200) shown in FIG.

  The frame aggregation unit 301 is a unit that aggregates a set number of transmission data and creates an aggregation frame. The frame transmission unit 302 is a unit that transmits the created aggregation frame to another wireless LAN device that is a counterpart station. As described above, the frame aggregating unit 301 is an example of an aggregating unit that aggregates a plurality of pieces of transmission data into the first frame transmitted to the second communication device. The frame transmission unit 302 is an example of a frame transmission unit.

  The reception status monitor 303 is a unit that acquires the reception status at other stations regarding the frames transmitted from the own station based on the number of frames transmitted from the own station to the other station. The reception status monitor 303 is a reception status acquisition unit that acquires the reception status in the second communication device for the frame transmitted from the first communication device based on the number of frames transmitted from the first communication device to the second communication device. It is an example. The reception status monitor 303 is an example of an acquisition unit that acquires the reception status in the second communication device for the first frame transmitted from the first communication device.

  The transmission frame counter 304 is a unit that counts the number of frames transmitted from the own station. Thus, the transmission frame counter 304 is an example of a transmission frame counting unit that counts the number of frames transmitted from the first communication device.

  The confirmation response counter 305 is a unit that counts the number of confirmation responses received for the frame transmitted by the local station. The confirmation response counter 305 is an example of a confirmation response counting unit that counts the number of confirmation responses received for a transmitted frame.

  Normally, the partner station transmits an acknowledgment (so-called Ack) every time a frame is received. This is an index for the transmission side apparatus to determine whether or not the transmitted frame is received without error. For example, if the count value of the confirmation response counter 305 is smaller than the count value of the transmission frame counter 304, it means that some of the transmitted frames have not been received. In rare cases, the transmitted side may not receive an acknowledgment even if the transmitted frame is correctly received by the receiving side.

  Note that the reception status monitor 303 may acquire the reception status at the local station regarding frames transmitted from other stations based on the number of frames received by the local station from the partner station. For example, if the reception frame counter 306 counts the number of frames received from the other station by the frame reception unit 307, the rough transmission path condition can be determined from the count value. As described above, the reception status monitor 303 acquires the reception status in the first communication device for the frame transmitted from the second communication device based on the number of frames received by the first communication device from the second communication device. It is an example of a situation acquisition means. The received frame counter 306 is an example of a received frame counting unit that counts the number of frames received from the second communication device.

  The comparison unit 308 is a unit that compares the reception status of the local station with the reception status of other stations. For example, the comparison unit 308 can determine the superiority or inferiority of the reception status of the local station and the reception status of other stations by comparing the number of received frames with the number of transmitted frames. Therefore, the comparison unit 308 is an example of a comparison unit. The comparison unit 308 is also an example of superiority / inferiority determination means.

  The aggregation control unit 309 is a unit that controls the number of transmission data aggregated into an aggregation frame according to the comparison result of the reception status. For example, the aggregation control unit 309 maintains the number of transmission data aggregated in the aggregation frame if the reception status at the other station is better than the reception status at the local station. Further, the aggregation control unit 309 may reduce the number of transmission data aggregated in a frame if the reception status at the other station is worse than the reception status at the own station (if it is not good). In this case, the number of transmission data aggregated in the aggregation frame can also be referred to as the aggregation length. In general, the longer the aggregation length, the higher the possibility of receiving an error, and the shorter the aggregation length, the lower the possibility of receiving an error. Thus, the aggregation control unit 309 is an example of a number control unit that maintains, decreases, or increases the number of transmission data aggregated in a frame.

  The transmission rate control unit 310 is a unit that controls the transmission rate of the aggregation frame according to the comparison result of the reception status. In general, the higher the transmission rate, the higher the possibility of receiving an error, and the lower the transmission rate, the lower the possibility of receiving an error. For example, the transmission rate control unit 310 maintains the frame transmission rate if the reception status at the other station is better than the reception status at the local station. Also, the transmission rate control unit 310 reduces the frame transmission rate if the reception status at the other station is worse than the reception status at the local station. As described above, the transmission rate control unit 310 is an example of a transmission rate control unit that maintains, decreases, or increases the transmission rate of the aggregation frame.

  Note that the aggregation control unit 309 and the transmission rate control unit 310 may start the operation by using a decrease in the number of received acknowledgments as compared to the number of transmitted frames. That is, when it is estimated that the transmission status of the local station or the reception status of other stations has deteriorated, the aggregation control unit 309 and the transmission rate control unit 310 start operation.

  FIG. 4 is an exemplary block diagram illustrating functions provided in the wireless LAN device according to the embodiment. Here, each part shall be mainly implement | achieved by CPU200. Note that the same reference numerals are assigned to the units common to the units shown in FIG. 3 to simplify the description. The retransmission counter 401 and the retransmission success rate calculation unit 402 may be added to the block diagram shown in FIG.

  The reception status monitor 303 is an example of a determination unit that determines a successful retransmission status of the first frame from the first communication device to the second communication device. The reception status monitor 303 includes a retransmission counter 401, a retransmission success rate calculation unit 402, and the above-described confirmation response counter 305 in order to determine the retransmission success status of the first frame. The retransmission counter 401 is a unit that counts the number of aggregation frames retransmitted by the frame transmission unit. Note that the frame transmission unit 302 retransmits a frame in which the corresponding confirmation response could not be received from the counterpart station among the transmitted frames. Which aggregation frame should be retransmitted can be specified by a sequence number or the like mounted in the retransmission request transmitted from the partner station. As described above, the frame transmission unit 302 is an example of a retransmission unit that retransmits a frame for which an acknowledgment could not be received.

  The retransmission success rate calculation unit 402 calculates the success rate of the retransmitted frame. For example, the retransmission success rate calculation unit 402 calculates the success rate by dividing the count value of the confirmation response by the count value of the retransmitted frame. Thus, the retransmission success rate calculation unit 402 is an example of a success rate calculation unit.

  The comparison unit 308 compares the success rate of the retransmitted frame with a predetermined threshold value. The threshold is preferably set to a value that maximizes the throughput empirically. For example, if the success rate of the retransmitted frame exceeds the threshold value, the aggregation control unit 309 maintains the number of transmission data (aggregation length), and the transmission rate control unit 310 decreases the transmission rate. On the other hand, if the success rate of the retransmitted frame is less than or equal to the threshold, the aggregation control unit 309 decreases the number of transmission data, and the transmission rate control unit 310 maintains the transmission rate.

  FIG. 5 is a diagram for explaining an example of a frame when frame aggregation is not executed. When aggregation is not executed, the corresponding transmission headers 503, 505, and 507 and frame checks 504, 506, and 508 are added to the three transmission data 500, 501, and 502, and frames 509, 510, and 511 are created. .

  FIG. 6 is a diagram for explaining an example of a frame when frame aggregation is performed. Here, it is assumed that the aggregation length is 3. The three transmission data 600, 601, and 602 are assigned one corresponding header 603 and one frame check 604, and an aggregation frame 609 is created. As can be seen from the comparison with FIG. 5, overhead such as header and frame check is reduced, so that throughput is improved.

  FIG. 7 is a sequence diagram illustrating an example of the embodiment. Here, it is assumed that the STA 102 operates as a transmission side (own station), and the STA 103 operates as a reception side (counter station). As an example, the transmission rate control unit 310 sets 600 Mbps as the initial transmission rate in the frame transmission unit 302. Also, the aggregation control unit 309 sets the aggregation length to 3. These specific numerical values are merely examples.

  In S700, the frame aggregation unit 301 aggregates three pieces of transmission data to create an aggregation frame, and the frame transmission unit 302 transmits the aggregation frame to the STA 103 at the set transmission rate. The transmission counter increments the count value by one.

  In step S <b> 701, when the CPU 200 of the STA 103 receives the aggregation frame, the CPU 200 transmits an Ack indicating that the aggregation frame is correctly received to the STA 102. The acknowledgment counter increments the count value by one.

In S702, the CPU 200 of the STA 102 calculates the reception rate of the local station, and compares the calculated reception rate with the lower limit value R _Low and the upper limit value R _High . An arithmetic example of the reception rate of the own station will be described later.

Normally, if the reception rate of the local station exceeds the upper limit value R _High , the CPU 200 increases the aggregation length and the transmission rate. If the reception rate of the local station is not less than the lower limit value R _{Low and not} more than the upper limit value R _High , the CPU 200 maintains the aggregation length and the transmission rate. If the reception rate of the local station is less than the lower limit value R _Low , it means that the reception status of the local station is deteriorated, and therefore the CPU 200 requests the reception status from the STA 103 which is the counterpart station. This request may include the number N of aggregation frames transmitted by the STA 102.

  In S <b> 703, when the CPU 200 of the STA 103 receives a request for the reception status of the aggregation frame from the STA 102, the CPU 200 transmits a report loaded with the reception status of the aggregation frame to the STA 102. The reception status can be expressed using the number N of aggregation frames transmitted by the STA 102 and the number M of aggregation frames received by the STA 103 during a certain period. That is, the reception rate = M / N.

  In S <b> 704, the CPU 200 of the STA 102 extracts the reception rate of the partner station from the received report and compares it with the threshold value P. Here, the CPU 200 functions as a comparison unit that compares the reception status in the second communication device acquired by the acquisition unit with a predetermined value P. Note that the threshold value P may be a reception rate of the own station or may be a value obtained in advance by experience. The reception rate of the own station can be expressed using the number A of confirmation responses received from the partner station. That is, the reception rate of the local station is reception rate = A / N. N is the number of aggregation frames transmitted by the STA 102 during a certain period. Here, it is assumed that the receiving rate of the partner station is larger than P. Therefore, the CPU 200 of the STA 102 maintains the aggregation length and the transmission rate.

  In S705, the CPU 200 of the STA 102 sets the current transmission rate as the initial transmission rate. The initial transmission rate is a transmission rate applied when the first frame is transmitted. The first frame is merely a name for distinguishing it from the retransmission frame. That is, if Ack is not returned for the first frame, the first frame stored in the buffer (memory 201) is read again and transmitted as a retransmission frame.

  In S706, the STA 102 creates and transmits the next aggregation frame. In step S707, the STA 102 returns Ack because the reception is successful.

  Thus, if the reception status of the counterpart station is not deteriorated, the aggregation length and the transmission rate are maintained. Of course, the CPU 200 may increase at least one of the aggregation length and the transmission rate.

  FIG. 8 is a sequence diagram illustrating an example of the embodiment. The same reference numerals are assigned to portions common to those in FIG. 7 to simplify the description. For example, descriptions of S700 to S703 and S707 are omitted.

  In S804, the CPU 200 of the STA 102 compares the reception rate of the partner station with the threshold value P, and recognizes that the reception rate of the partner station is equal to or less than the threshold value P. Furthermore, the CPU 200 determines the retransmission success status of the local station. Here, the retransmission success status is a retransmission success rate. Therefore, the CPU 200 calculates the retransmission success rate of the local station and compares it with the threshold value Q. The retransmission success rate of the local station is, for example, the number of transmissions i of the same aggregation frame including retransmissions during a certain period and the number of receptions j of confirmation responses. In this case, the transmission success rate including the retransmission of the aggregation frame is j / i. The threshold value Q is set, for example, by empirically obtaining a value that provides the best data transfer efficiency in the actual environment. Here, it is assumed that the transmission success rate including retransmission is larger than the threshold value Q. Therefore, the CPU 200 reduces the transmission rate by a predetermined amount while maintaining the aggregation length. Here, the predetermined amount is 60 Mbps. The reduced transmission rate is 540 Mbps.

  In S805, the CPU 200 of the STA 102 sets the current transmission rate (540 Mbps) as the initial transmission rate. In S806, the CPU 200 transmits the aggregation frame by applying 540 Mbps as the transmission rate.

  Thus, if the reception status of the other station is deteriorated, the error rate can be improved by reducing the transmission rate at least. CPU 200 may dynamically calculate the amount of decrease in the transmission rate from the reception rate.

  FIG. 9 is a sequence diagram illustrating an example of the embodiment. The same reference numerals are assigned to portions common to those in FIG. 7 to simplify the description. For example, descriptions of S700 to S703 and S707 are omitted.

  In S904, the CPU 200 of the STA 102 compares the reception rate of the counterpart station with the threshold value P, and recognizes that the reception rate of the counterpart station is equal to or less than the threshold value P. Further, the CPU 200 calculates a transmission success rate including the retransmission of the local station and compares it with the threshold value Q. Here, it is assumed that the transmission success rate including retransmission is equal to or less than the threshold value Q. The CPU 200 maintains the transmission rate while reducing the aggregation length. For example, the aggregation length is reduced from the initial 3 to 2.

  In S905, the CPU 200 of the STA 102 sets the current transmission rate (600 Mbps) as the initial transmission rate. In S906, the CPU 200 assembles the aggregation frame according to the reduced aggregation length, and transmits the aggregation frame by applying 600 Mbps as the transmission rate.

  In this way, when the reception rate of the own station decreases, the reception rate of the counterpart station also decreases, and the retransmission success rate also decreases, maintaining the transmission rate while reducing the aggregation length, the communication error is reduced. Try to improve. Even if the reception rates of the local station and other stations are reduced, the transmission rate may be increased while maintaining the aggregation length as long as the transmission success rate including retransmission is not reduced.

  FIG. 10 is a flowchart illustrating an example of a control method according to the embodiment. Each step is executed by the above-described CPU 200 and various units (FIGS. 3 and 4) realized by the CPU 200. Note that the flowchart shown in FIG. 10 shows processing when all options according to the present invention are installed. Therefore, some of the steps described below may be omitted. For example, S1001, S1016, and S1017 may be omitted. Steps S1009, S1012, and S1013 may be omitted. Alternatively, steps S1009, S1010, and S1011 may be omitted.

  In step S1001, the CPU 200 determines whether the current transmission of the aggregation frame is the first transmission or the retransmission. Normally, the CPU 200 stores the number of retransmissions for each frame in the memory, and therefore can determine whether or not it is the first time by reading the number of retransmissions from the memory. If it is the first time, the process proceeds to step S1002. If it is resending, it will progress to step S1016.

In step S1002, the CPU 200 calculates a reception rate for the Ack received with respect to the aggregation frame transmitted by the local station, and compares it with the lower limit value R _Low and the upper limit value R _High . As a result of the comparison, if the Ack reception rate of the own station is not less than the lower limit value R _{Low and not} more than the upper limit value R _High , the process proceeds to step S1005. As a result of the comparison, if the Ack reception rate of the local station is less than the lower limit value R _Low , the process proceeds to step S1003. As a result of the comparison, if the Ack reception rate of the local station exceeds the upper limit value R _High , the process proceeds to step S1014.

  In step S1003, CPU 200 obtains the reception rate of the counterpart station, which is an example of the second communication device. For example, the CPU 200 receives a reception rate report from the counterpart station by transmitting a reception rate request to the counterpart station. The reception rate report includes information on the reception rate of the aggregation frame received by the partner station. When the other station (STA 103) knows the number of frames transmitted by the own station (STA 102), the other station calculates the reception rate and mounts it in the reception rate report. On the other hand, when the partner station (STA 103) does not know the number of frames transmitted by the own station (STA 102), the partner station mounts the number of frames received within a certain period in the reception rate report. As described above, when the reception rate report includes information on the number of aggregation frames received by the counterpart station, the CPU 200 calculates the reception rate of the counterpart station by dividing by the number of aggregation frames transmitted by the own station. To do. Thus, the reception status is information based on the first frame number transmitted from the first communication device to the second communication device in a certain period and the first frame number received in the certain period by the second communication device.

  In step S1004, CPU 200 determines whether or not the reception rate of the partner station exceeds threshold value P. If it exceeds, the process proceeds to step S1005. On the other hand, if not, the process proceeds to step S1009.

  In step S1005, CPU 200 maintains the current aggregation length as it is. In step S1006, CPU 200 maintains the initial transmission rate as it is. Note that steps S1005 and S1006 may be omitted because the aggregation length and the transmission rate are not changed. As described above, when the reception status in the second communication apparatus is larger than the predetermined value P as a result of the comparison by the comparison unit, the CPU 200 does not decrease the transmission rate of the first frame and the number of transmission data aggregated in the first frame. To control. Thereafter, the process proceeds to step S1007. The values of the current aggregation length, the current transmission rate, and the initial transmission rate are stored in the memory and are read and written by the CPU 200. An example in which the aggregation length and the transmission rate are not changed is as shown in FIG.

  In step S1007, CPU 200 sets the currently set transmission rate as the initial transmission rate. In step S1008, CPU 200 transmits an aggregation frame by applying the currently set transmission rate. Thereafter, if the next transmission target frame remains, the process returns to step S1000. If not, the process of this flowchart ends.

  By the way, if the reception rate of the partner station is equal to or less than the threshold P in step S1004, the process proceeds to step S1009. In step S1009, the CPU 200 calculates a transmission success rate including retransmission of the local station, and determines whether or not the transmission success rate including the calculated retransmission exceeds a threshold value Q. If it has exceeded, the process proceeds to step S1010. If not, the process proceeds to step S1012.

  In step S1010, CPU 200 maintains the aggregation length. In step S1011, the CPU 200 decreases the initial transmission rate by a predetermined amount (eg, 60 Mbps). That is, the CPU 200 changes the data of the initial transmission rate stored in the memory. Thereafter, the process proceeds to step S1007.

  As described above, when the transmission success rate including the retransmission exceeds the threshold, the partner station can successfully receive the packet by retransmitting the frame having the current aggregation length several times. Therefore, the current aggregation length is maintained. However, since retransmission is necessary, the reception rate of the other station is improved by temporarily reducing the transmission rate. In this way, the case where the aggregation length is maintained and the transmission rate is reduced is as shown in FIG.

  Therefore, the CPU 200 is also an example of a transmission unit that reduces the transmission rate of the first frame without reducing the number of transmission data aggregated in the first frame. That is, when the successful retransmission status is larger than the predetermined value Q, the CPU 200 decreases the transmission rate of the first frame without decreasing the number of transmission data aggregated in the first frame.

  By the way, if the transmission success rate including the retransmission of the own station is equal to or less than the threshold Q in step S1009, the process proceeds to step S1012. In step S1012, CPU 200 decreases the aggregation length by a predetermined amount. In step S1013, CPU 200 maintains the initial transmission rate.

  In this way, when the transmission success rate including retransmission is below the threshold, it is unlikely that the other station will succeed in receiving the frame even if the current aggregation length frame is retransmitted several times. Therefore, the CPU 200 attempts to improve the reception status of the counterpart station by reducing the current aggregation length. This will be particularly effective in an environment where reducing the aggregation length is more effective than reducing the transmission rate. In this way, the case where the aggregation length is reduced and the transmission rate is maintained is as shown in FIG.

  When the reception status in the second communication apparatus is smaller than the predetermined value P as a result of the comparison by the comparison means, the CPU 200 reduces the number of transmission data to be aggregated in the first frame according to the retransmission success status. It is an example. At this time, the CPU 200 may not decrease the transmission rate of the first frame. As described above, when the successful retransmission status determined by the determination unit is smaller than the predetermined value Q, the CPU 200 decreases the number of transmission data aggregated in the first frame without decreasing the transmission rate of the first frame.

By the way, if the Ack reception rate of the local station exceeds the upper limit value R _High in step S1002, the process proceeds to step S1014. In step S1014, the CPU 200 increases the aggregation length by a predetermined amount. In step S1015, CPU 200 increases the initial transmission rate by a predetermined amount. Thus, if the Ack reception rate of the own station exceeds the upper limit value R _High , it can be estimated that the reception rate of the aggregation frame at the counterpart station is also high. Therefore, in order to improve the throughput, it is preferable to increase both the aggregation length and the initial transmission rate. That is, the number of confirmation responses to the first frame from the second communication device received by the first communication device over a certain period is greater than the number of first frames transmitted from the first communication device to the second communication device over a certain period. Is detected to exceed a certain percentage. When the number of confirmation responses exceeds a certain ratio than the first frame number, the CPU 200 increases the transmission rate of the first frame and increases the number of transmission data aggregated in the first frame.

  By the way, when it is determined in step S1001 that retransmission, the process proceeds to step S1016. In step S1016, the aggregation length used for the initial transmission is read from the memory, and is set as the aggregation length for the current retransmission. That is, the aggregation length used for the initial transmission is the same as the aggregation length used for the current retransmission. In step S1017, CPU 200 reads the previous transmission rate from the memory, and sets a value obtained by reducing the previous transmission rate by a predetermined amount as the current transmission rate. That is, at the time of retransmission, the transmission rate is decreased by a predetermined amount. As described above, when retransmitting the first frame, the CPU 200 may decrease the transmission rate of the first frame without reducing the number of transmission data aggregated in the first frame.

  The various embodiments have been described above. For example, according to the present embodiment, since the reception status of the partner station and the reception status of the local station can be acquired without particularly modifying the existing protocol, it is easy to maintain the interoperability with existing equipment. Furthermore, according to the present embodiment, at least when the reception status of the partner station is relatively deteriorated, the number of transmission data aggregated in a frame is adjusted. Therefore, it is possible to suppress a decrease in throughput due to environmental changes.

  In addition, by controlling the transmission rate instead of the aggregation length or together with the aggregation length, it is possible to more flexibly suppress a decrease in throughput due to environmental changes. For example, there may be situations where it is easier to improve the throughput by changing the transmission rate than by changing the aggregation length. Conversely, there may be situations where it is difficult to improve throughput unless the transmission rate is changed in addition to the aggregation length. Therefore, it seems important to control communication parameters flexibly according to the environment.

  By counting the number of transmitted aggregation frames and the number of confirmation responses, it becomes easy to grasp the changes in the reception status of the own station and the transmission status of other stations. In particular, these parameters are considered to be effective as triggers for starting the number control and the transmission rate control. As described above, the CPU 200 may detect a predetermined trigger and perform change control of the number of transmission data aggregated in the first frame or transmission rate change control. As the predetermined trigger, for example, the confirmation of the first frame from the second communication device received by the first communication device in a certain period rather than the number of first frames transmitted from the first communication device to the second communication device in the certain period. The number of responses has fallen below a certain percentage.

  Also, to determine the superiority or inferiority of the reception status of the local station and the reception status of the other station, compare the number of frames transmitted by the local station to the other station and the number of frames received by the local station from the other station. Is preferred. Such a determination is considered to be particularly effective between two wireless communication apparatuses that transmit and receive substantially the same number of frames.

  Further, attention may be paid to the transmission success rate of frames including retransmission. For example, if the transmission success rate of frames including retransmission exceeds a threshold, the aggregation length may be maintained and the transmission rate may be reduced. Further, if the success rate of the retransmitted frame is equal to or less than the threshold, the aggregation length may be reduced and the transmission rate may be maintained. Thus, since the transmission success rate including retransmission is affected by the aggregation length and the transmission rate, it is considered important to select parameters to be controlled according to the success rate at that time.

It is a figure which shows an example of the radio | wireless communications system which concerns on embodiment. 1 is an exemplary block diagram of a wireless LAN device according to an embodiment. It is the exemplary block diagram which showed the function with which the wireless LAN apparatus which concerns on embodiment is provided. It is the exemplary block diagram which showed the function with which the wireless LAN apparatus which concerns on embodiment is provided. It is a figure for demonstrating an example of the flame | frame when a frame aggregation is not performed. It is a figure for demonstrating an example of a frame in case frame aggregation is performed. It is a sequence diagram which shows an example of embodiment. It is a sequence diagram which shows an example of embodiment. It is a sequence diagram which shows an example of embodiment. It is the flowchart which showed an example of the control method which concerns on embodiment.

Claims (9)

A first communication device comprising:
Aggregation means for aggregating a plurality of transmission data in a first frame transmitted to the second communication device;
Obtaining means for obtaining a reception status in the second communication device for the first frame transmitted from the first communication device;
Determining means for determining a successful retransmission status of the first frame from the first communication device to the second communication device;
Comparing means for comparing the reception status in the second communication device acquired by the acquiring means with a predetermined value P;
If the reception status at the second communication device is smaller than the predetermined value P as a result of the comparison by the comparison means, the transmission rate of the first frame is decreased according to the retransmission success status determined by the determination means. Transmission means for reducing the transmission rate of the first frame without reducing the number of transmission data aggregated in the first frame without reducing the number of transmission data aggregated in the first frame. A featured first communication device.   The transmission means reduces the number of transmission data aggregated in the first frame without reducing the transmission rate of the first frame when the retransmission success status determined by the determination means is smaller than a predetermined value Q. The transmission rate of the first frame is reduced without reducing the number of transmission data aggregated in the first frame when the successful retransmission status is larger than a predetermined value Q. 1st communication apparatus.   The first communication device according to claim 1, wherein the acquisition unit acquires the reception status from the second communication device.   The reception status is information based on the first frame number transmitted from the first communication device to the second communication device in a certain period and the first frame number received in the certain period by the second communication device. The first communication device according to claim 1, wherein the first communication device is a first communication device.   The transmitting means is configured to receive the first communication device from the second communication device that the first communication device has received in the certain period of time than the first number of frames transmitted from the first communication device to the second communication device in the certain period. The control of changing the number of transmission data to be aggregated in the first frame or changing the transmission rate is triggered by the fact that the number of confirmation responses for one frame is equal to or less than a certain ratio. Item 5. The first communication device according to any one of Items4.   If the reception state in the second communication device is greater than the predetermined value P as a result of the comparison by the comparison unit, the transmission unit has a transmission rate of the first frame and a number of transmission data to be aggregated in the first frame. The first communication device according to claim 1, wherein the first communication device is not decreased.   The transmitting means is configured to receive the first communication device from the second communication device that the first communication device has received in the certain period of time than the first number of frames transmitted from the first communication device to the second communication device in the certain period. The transmission rate of the first frame is increased and the number of transmission data aggregated in the first frame is increased when the number of confirmation responses for one frame exceeds a certain ratio. The first communication device according to claim 6.   The transmission means, when retransmitting the first frame, reduces the transmission rate of the first frame without reducing the number of transmission data aggregated in the first frame. The first communication device according to any one of claims 1 to 7. A communication method in a first communication device that aggregates and transmits a plurality of transmission data in a first frame transmitted to a second communication device,
An acquisition step of acquiring a reception status in the second communication device for the first frame transmitted from the first communication device;
A determination step of determining a successful retransmission status of the first frame from the first communication device to the second communication device;
When the reception status in the second communication device is smaller than a predetermined value P, the transmission rate of the first frame is aggregated into the first frame according to the successful retransmission status determined in the determination step. A transmission step of reducing the transmission rate of the first frame without reducing the number of transmission data or transmitting without reducing the number of transmission data aggregated in the first frame;
The communication method in the 1st communication apparatus characterized by having.

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