JP2016189583A - Transmitter, transmission method, and program - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance followability of a MCS, when the quality of a communication path changes in the way of communication.SOLUTION: A transmitter raises a MCS to a high level, when the number of times n of transmission success in units of frame, or a value n' based thereon goes above a first threshold by an adaptive rate control section, increases the first threshold when transmission in units of frame fails immediately after the MCS is raised to a high level, and decreases the first threshold when the number of times n of transmission success in units of frame, or the value n' based thereon goes above a second threshold. The disclosure is applicable to a wireless communication system.SELECTED DRAWING: Figure 7

Description

  The present disclosure relates to a transmission device, a transmission method, and a program, and in particular, a transmission device, a transmission method, and a program that adaptively change MCS (Modulation and Coding Scheme) according to communication conditions. About.

  Some existing wireless communication systems perform transmission by adaptively switching one of MCSs prepared in advance, which is estimated to be optimal, depending on the communication status. Usually, among the MCSs that are prepared, the lower the data transmission speed, the lower the communication path, the more successful the communication, but the higher the data transmission speed, the more successful the communication. Requires a high-quality communication path.

  If the transmission side of the communication system can directly know the quality of the communication path, adaptive MCS switching according to the communication status is easy. However, when the transmission side cannot directly know the quality of the communication path, there is a method of estimating the communication status based on the ACK frame transmitted from the reception side and switching the MCS according to the estimation result.

  Based on the ACK frame from the receiving side, the adaptive rate control technology that estimates the success or failure of transmission of a frame, which is a data transmission unit, and switches MCS according to the continuous number of successful transmissions is wireless based on the IEEE 802.11 standard ARF (Automatic Rate Fallback) (for example, see Non-Patent Document 1) used in the system and AARF (Adaptive ARF) (for example, see Non-Patent Document 2), which is an extension of ARF, are known. There is also an adaptive rate control technique that estimates the success or failure of frame transmission based on an ACK frame from the receiving side, and switches MCS according to the transmission failure rate of transmission in a past fixed time (see, for example, Patent Document 1). ).

JP 2003-51781 A

A. Kamerman and L. Monteban, “WaveLAN-II: A High-Performance Wireless LAN for the Unlicensed Band”, Bell Labs Technical Journal, pp. 118-133, Summer 1997. M. Lacage, M. H. Manshaei, and T. Turletti. "IEEE802.11 Rate Adaptation: A Practical Approach". INRIA Research Report number 5208, May2004.

  FIG. 1 is a flowchart for explaining adaptive rate control processing (hereinafter referred to as AARF processing) by AARF. Note that if the processing in steps S13 and S20 is omitted from the figure, the flowchart explains the adaptive rate control processing by ARF (hereinafter referred to as ARF processing). FIG. 2 shows the meanings and initial values of symbols representing thresholds and variables in the flowchart of FIG.

An overview of ARF processing and AARF processing will be described. In the ARF processing, when the number n of successful transmissions of a frame, which is a data transmission unit, is equal to or greater than a threshold value a (a is a fixed value, FIG. 1 shows an example of the threshold value a = a _min ). , MCS is changed to a level one level higher than the current level (a level at which the data transfer rate is fast). Also, if the frame transmission fails immediately after the MCS is changed to a level higher by one level, or if the frame transmission fails m times consecutively, the MCS is one level lower than the current level (the data transfer rate is slow). Level). Further, regardless of the success or failure of frame transmission, the MCS is changed to a level higher by one step when the frame transmission count t becomes equal to or greater than the threshold value g. The success or failure of frame transmission on the transmission side is determined based on whether or not the ACK frame from the reception side can be received.

On the other hand, in the AARF process, as in the ARF process, when the number of consecutive successful frame transmissions n is greater than or equal to a threshold value a (a is variable from a _min to a _max ), the MCS is one level higher than the current level. Be changed. In addition, when the frame transmission fails immediately after the MCS is changed to a level one step higher, or when the frame transmission fails m times continuously, the MCS is changed to a level one step lower than the current level. Furthermore, regardless of the success or failure of frame transmission, when the number of consecutive transmissions t in the same MCS becomes equal to or greater than the threshold value g, the MCS is changed to a level one step higher.

However, in the AARF processing, if the transmission of a frame fails immediately after the MCS is changed to a level higher by one level, and the MCS is changed to a level lower by one level, as long as the threshold value a is less than _amax , k ₁ Will be doubled.

  According to the ARF processing, the transmission side can adaptively control the transmission rate only with the ACK frame from the reception side. Therefore, ARF processing can be applied to many wireless standard products. However, since the ARF process is executed, there is a possibility that the frame transmission success probability deteriorates when the quality of the communication channel is stable as compared with the case where the ARF process is not executed.

FIG. 3 is a specific example of the problem described above, and is an example of a simulation result of the MCS transmission frame number dependency in the ARF process when the communication quality is constant. There are 6 levels from mcs0 to mcs5 in order from the lowest MCS level, and PER (Packet Error Rate) is close to 0 from the bottom to the 4th mcs3, and mcs4 is one level higher than that. Assume that PER is 1. The initial value a _min of the threshold value a is set to 10.

  In this case, in mcs3, there is a very high possibility that the continuous number n of successful frame transmissions will be 10 or more, which is the threshold value a. In this case, MCS is changed to mcs4. However, if MCS is changed to mcs4, frame transmission fails immediately after that, so MCS is returned to mcs3. If there is no change in the assumed quality of the communication path, such MCS change is repeated. In this case, the transmission success probability of the frame is 1 if the ARF process is not executed, but is deteriorated to a / (a + 1) (= 10/11) because the ARF process is executed. This degradation can be mitigated by increasing the threshold value a, but in this case, the initial pull-in performance of MCS and the follow-up performance when the quality of the communication channel is improved during communication are degraded.

FIG. 4 shows an example of a simulation result of the MCS transmission frame number dependency by AARF processing when the communication quality is constant. As in Fig. 3, the MCS level has six levels from mcs0 to mcs5 in order from the lowest, PER is close to 0 from the bottom to the fourth mcs3, and is one level higher than mcs4. Assume that PER is 1. Also, the initial value a _min = 10 of the threshold value a, the maximum value a _max = 50, the initial value g _min = 250 of the threshold value g, and the coefficient k ₁ = 2 are set.

In this case, up to mcs3 increases in the same manner as in the ARF processing, but is changed from mcs3 to mcs4, and immediately after that, when frame transmission fails and returns to mcs3, the threshold value a is the initial value a _min × k ₁ = 20 Next, when mcs3 is changed to mcs4, and immediately after that, when the frame transmission fails and is returned to mcs3, the threshold a is doubled to 40. Further, when the frame is changed from mcs3 to mcs4 and immediately after that, transmission of the frame fails and the flow returns to mcs3, the threshold value a is changed to the upper limit value of 50. When the threshold value a reaches the upper limit value of 50, the transmission success probability of subsequent frames is 50/51 = 98%.

  As described above, the ARF processing frame transmission success probability when the initial value of the threshold value a is the same is 10/11 = 90.9%. Therefore, in the AARF processing, the frame transmission is compared with the ARF processing. The success probability can be improved by 7.1%. Further, when the initial value of the threshold value a for AARF processing and ARF processing is the same, the initial pull-in performance of MCS does not deteriorate.

  Therefore, in the AARF process, compared to the ARF process, the frame transmission success probability can be improved without causing deterioration of the initial pull-in performance of MCS.

  However, even with AARF processing, the tracking performance of MCS when the channel quality is improved during communication may be inferior to that of ARF processing. This will be specifically described with reference to FIGS.

FIG. 5 shows an example of the simulation result of the MCS transmission frame number dependency by ARF processing when the communication quality is improved during communication, and FIG. 6 shows an example of the simulation result by AARF processing when the communication quality is improved during communication. , Each showing. 5 and 6, there are 6 levels from mcs0 to mcs5 in order from the lowest MCS level, and until 120 frames are transmitted, PER is a value close to 0 until the 4th mcs3 from the bottom. It is also assumed that PER is 1 at mcs4 which is one step higher than that. It is assumed that the quality of the communication channel is improved after 120 frames are transmitted, and PER is close to 0 even for mcs4 and mcs5. Also, the initial value a _min = 10 of the threshold value a, the maximum value a _max = 50, the initial value g _min = 250 of the threshold value g, and the coefficient k ₁ = 2 are set.

In the case of ARF processing, as shown in FIG. 5, when transmitting about 140 frames, it is raised to mcs5 and stabilized as it is. However, in the AARF process, the threshold value a reaches the maximum value a _max due to a transmission failure before 120 frames are transmitted, so that it is increased to mcs5 only when 200 frames are transmitted.

That is, in the AARF process, the maximum convergence time of MCS when the channel quality is improved during communication is (a _max −a _min ) / a _min (4 in the above example) deterioration (extension) compared to the ARF process. ).

  In the adaptive rate control technique disclosed in Patent Document 1, a transmission failure rate r is calculated from the number of frame transmissions and the number of transmission failures in the past fixed time, and if the failure probability r is less than the threshold p, MCS Is changed to a rate one step higher than the current level. On the other hand, if the failure probability r is equal to or greater than the threshold q, the MCS is changed to a lower rate that is one step lower than the current rate.

  As described above, in the adaptive rate control technique of Patent Document 1, since the rate is controlled based on the transmission failure rate r, it is more accurate than ARF processing that controls the rate based on the number of consecutive transmission successes or the number of consecutive failures. Rate control is possible. That is, when MCS is optimal, communication is stable in a range where the transmission failure rate r is larger than the threshold value p and smaller than the threshold value q, and the MCS is not changed. There is a high possibility that no rate degradation will occur when the is stable. Furthermore, when the communication quality is improved during communication, the convergence time at that time can achieve the same performance as the initial state.

  However, in order to optimize the MCS, depending on the communication system to be used, if the threshold value p is not set to a relatively small value, the MCS is alternately repeated at a level that is different by one step every predetermined time, and the transmission success rate is increased. There may be a period that becomes a minimum of 1/2 before the control. If the threshold value p is set to a relatively small value so as not to generate this period, the transmission failure rate r must be observed for a long time, and the convergence time becomes long.

  The present disclosure has been made in view of such a situation, and is intended to improve the follow-up performance of MCS when the quality of a communication path changes during communication.

  A transmission apparatus according to a first aspect of the present disclosure uses an adaptive rate control unit that controls MCS to be applied when transmitting data according to a communication state, and the MCS determined by the adaptive rate control unit. A transmission unit that modulates and encodes the data and transmits the transmission data obtained as a result in units of frames, and the adaptive rate control unit includes the number n of successful transmissions in units of frames or a value based on the number of successful transmissions n When n ′ is equal to or higher than the first threshold, the MCS is raised to a high level, and immediately after the MCS is raised to a high level, the transmission of the frame unit fails immediately after the MCS is raised to the high level. When the number of successful transmissions n per frame or the value n ′ based on the successful transmission times n becomes equal to or greater than a second threshold after increasing the MCS to a high level, the first threshold It is reduced.

  The second threshold value may be an initial value of the first threshold value.

  The adaptive rate control unit can lower the MCS to a lower level if transmission in the frame unit fails immediately after raising the MCS to a higher level.

  The adaptive rate control unit can determine success or failure of transmission in units of frames based on an ACK frame transmitted from the receiving side.

  A transmission method according to a first aspect of the present disclosure uses an adaptive rate control unit that controls MCS to be applied when transmitting data according to a communication situation, and the MCS determined by the adaptive rate control unit. In a transmission method of a transmission apparatus comprising: a transmission unit that modulates and encodes the data and transmits transmission data obtained as a result thereof in units of frames; the number n of successful transmissions in units of frames or the transmission by the adaptive rate control unit When the value n ′ based on the number of successes n is greater than or equal to the first threshold, the MCS is raised to a high level, and when transmission in the frame unit fails immediately after raising the MCS to a high level. After the first threshold value is increased and the MCS is raised to a high level, the number of successful transmissions n per frame or the value n ′ based on the successful transmission number n is the second threshold value. When it became above includes the step of reducing the first threshold.

  A program according to a first aspect of the present disclosure uses an adaptive rate control unit that controls MCS to be applied when transmitting data according to a communication situation, and uses the MCS determined by the adaptive rate control unit. A program for controlling a transmission apparatus comprising: a transmission unit that modulates and encodes data and transmits transmission data obtained as a result of each frame; the adaptive rate control unit includes: Alternatively, when the value n ′ based on the number of successful transmissions n is equal to or greater than a first threshold, the MCS is raised to a high level, and the transmission in units of frames fails immediately after the MCS is raised to a high level. In this case, after the first threshold value is increased and the MCS is raised to a high level, the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n is If equal to or more than threshold value to execute a process including the step of reducing the first threshold value to the computer of the transmitting device.

  In the first aspect of the present disclosure, when the number of successful transmissions n per frame or the value n ′ based on the successful transmission times n is equal to or greater than a first threshold, the MCS is raised to a high level, If the transmission in the frame unit fails immediately after the MCS is raised to a high level, the first threshold is increased, and after the MCS is raised to a high level, the number of successful transmissions n in the frame unit or the When the value n ′ based on the number of successful transmissions n is greater than or equal to the second threshold value, the first threshold value is decreased.

  A transmission apparatus according to a second aspect of the present disclosure uses an adaptive rate control unit that controls MCS to be applied when transmitting data according to a communication state, and the MCS determined by the adaptive rate control unit. A transmission unit that modulates and encodes the data and transmits the transmission data obtained as a result in units of frames, and the adaptive rate control unit includes the transmission failure probability r in units of frames or a value based on the transmission failure probability r When r ′ is less than the first threshold, the MCS is raised to a high level, and the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is greater than or equal to the second threshold. If the transmission in units of frames fails immediately after raising the MCS to a high level, the first threshold value is decreased, and the MCS is increased to a high level. The transmission failure probability r or the value r 'is in when it becomes less than the third threshold value to increase the first threshold after the pulled.

  The third threshold value may be an initial value of the first threshold value.

  The adaptive rate control unit may lengthen the calculation period of the transmission failure probability r when decreasing the first threshold and shorten the calculation period of the transmission failure probability r when increasing the first threshold. it can.

  The adaptive rate control unit can shorten the calculation period of the transmission failure probability r after raising the MCS to a high level.

  The adaptive rate control unit can initialize the calculation period of the transmission failure probability r after raising the MCS to a high level.

  A transmission method according to a second aspect of the present disclosure uses an adaptive rate control unit that controls MCS to be applied when transmitting data according to a communication state, and the MCS determined by the adaptive rate control unit. In a transmission method of a transmission apparatus comprising: a transmission unit that modulates and encodes the data and transmits transmission data obtained as a result in units of frames; the transmission failure probability r in units of frames or the transmission by the adaptive rate control unit When the value r ′ based on the failure probability r becomes less than the first threshold, the MCS is raised to a high level, and the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is the first value. When the threshold value of 2 or more is reached, the MCS is lowered to a low level, and immediately after the MCS is raised to a high level, the transmission in the frame unit fails immediately after the MCS is raised to a high level. It decreases the value, the if the transmission failure after pulling up a high level MCS probability r or the value r 'is less than the third threshold value comprises the step of increasing said first threshold value.

  A program according to a second aspect of the present disclosure uses an adaptive rate control unit that controls MCS to be applied when transmitting data according to a communication situation, and the MCS determined by the adaptive rate control unit. A transmission apparatus control program comprising: a transmission unit that modulates and encodes data and transmits transmission data obtained as a result in units of frames, wherein the adaptive rate control unit includes a transmission failure probability r in units of frames. Alternatively, when the value r ′ based on the transmission failure probability r is less than the first threshold, the MCS is raised to a high level, and the transmission failure probability r in units of frames or the value r based on the transmission failure probability r If 'is greater than or equal to the second threshold, the MCS is lowered to a lower level, and immediately after the MCS is raised to a higher level, if the transmission in units of frames fails, the previous A step of decreasing the first threshold and increasing the first threshold when the transmission failure probability r or the value r ′ is less than a third threshold after raising the MCS to a high level. The processing is executed by the computer of the transmission apparatus.

  In the second aspect of the present disclosure, when the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is less than a first threshold, the MCS is raised to a high level, When the transmission failure probability r in frame units or the value r ′ based on the transmission failure probability r is equal to or greater than the second threshold, the MCS is lowered to a low level and immediately after the MCS is raised to a high level. When the transmission in the frame unit fails, the first threshold is decreased, and the transmission failure probability r or the value r ′ becomes less than the third threshold after the MCS is raised to a high level. If this happens, the first threshold value is increased.

  According to the first and second aspects of the present disclosure, it is possible to improve the followability of MCS when the quality of a communication path changes during communication.

It is a flowchart explaining an AARF process. It is a figure which shows the meaning and initial value of the symbol in FIG. It is a figure which shows the simulation result showing the malfunction by ARF process. It is a figure which shows the simulation result by AARF process. It is a figure which shows the simulation result by ARF process. It is a figure which shows the simulation result showing the malfunction by AARF process. It is a block diagram showing an example of composition of a transmitting device to which this indication is applied. It is a block diagram which shows the structural example of the adaptive rate control part of FIG. It is a flowchart for demonstrating a 1st adaptive rate control process. It is a flowchart for demonstrating a 1st adaptive rate control process. It is a figure which shows the meaning and initial value of the symbol in FIG. 9 and FIG. It is a figure which shows the simulation result by a 1st adaptive rate control process. It is a flowchart for demonstrating a 2nd adaptive rate control process. It is a figure which shows the meaning and initial value of the symbol in FIG. And FIG. 11 is a block diagram illustrating a configuration example of a general-purpose computer.

  Hereinafter, the best mode for carrying out the present disclosure (hereinafter referred to as an embodiment) will be described in detail with reference to the drawings.

<Configuration example of transmitting apparatus according to an embodiment of the present disclosure>
FIG. 7 illustrates a configuration example of the transmission apparatus according to the embodiment of the present disclosure. This transmission device 10 is configured to shorten the convergence time until convergence to the optimum MCS when the quality of the communication channel is improved during communication.

  The transmission device 10 includes an adaptive rate control unit 11, a transmission unit 12, and a reception unit 13. The adaptive rate control unit 11 determines the MCS to be used when the transmission unit 12 transmits data based on the adaptive rate determination information sequentially notified from the reception unit 13 and notifies the transmission unit 12 of the MCS. It is assumed that the adaptive rate determination information includes information indicating whether or not an ACK frame transmitted from the reception side that receives data transmitted by the transmission apparatus 10 is received.

  The transmission unit 12 modulates and encodes data to be transmitted using the MCS notified from the adaptive rate control unit 11, and wirelessly transmits the transmission data obtained as a result to the reception side. The receiving unit 13 receives an ACK frame transmitted from the receiving side. The receiving unit 13 sequentially notifies the adaptive rate control unit 11 of adaptive rate determination information including information indicating whether or not an ACK frame is received.

  FIG. 8 shows a detailed configuration example of the adaptive rate control unit 11. The adaptive rate control unit 11 includes a determination unit 21, a count unit 22, a threshold setting unit 23, a rate determination unit 24, and a probability calculation unit 25.

  The determination unit 21 determines success or failure of transmission of a frame (transmission unit of transmission data) based on the adaptive rate determination information from the reception unit 13. Moreover, the determination part 21 determines the relationship with respect to the threshold value of a variable. The count unit 22 initializes and counts various variables such as the number of consecutive successful frame transmissions n. The threshold setting unit 23 initializes and increases / decreases various thresholds. The rate determining unit 24 determines the MCS and notifies the transmitting unit 12 of it. The probability calculation unit 25 calculates a frame transmission failure rate.

<First Adaptive Rate Control Processing by Adaptive Rate Control Unit 11>
Next, the first adaptive rate control process by the adaptive rate control unit 11 will be described.

  9 and 10 are flowcharts illustrating the first adaptive rate control process. In the flowchart, symbols whose meanings and initial values are shown in FIG. 2 are used, and symbols whose meanings and initial values are shown in FIG. 11 are used.

  In step S31, the count unit 22 initializes various variables (initial values are substituted). Various threshold values are initialized by the threshold setting unit 23. In step S <b> 32, the number i assigned to represent the transmission order for the frame transmitted by the transmission unit 12 is incremented by 1 by the counting unit 22.

  In step S33, the transmission unit 12 transmits the i-th frame. In step S <b> 34, the determination unit 21 determines success or failure of transmission of the i-th frame transmitted in step S <b> 33 based on application rate determination information from the reception unit 13. If it is determined that the transmission is successful, the process proceeds to step S35.

  In step S35, the count unit 22 increments the frame transmission success number n by 1 and initializes the frame transmission failure number m to 0.

  In step S36, the determination unit 21 determines whether or not the number of consecutive successful frame transmissions n is equal to the threshold value b, and whether or not the current MCS has been increased by one level immediately before. If the determination result is affirmative (YES), the process proceeds to step S37, and if the determination result is negative (NO), step S37 is skipped.

In step S37, the threshold value setting unit 23 changes the threshold value a to a smaller value. Specifically, a value obtained by multiplying a small coefficient k ₃ than 1 to the state of the threshold value a, is compared initial value a _min threshold a is, the threshold a is changed to their greater value.

  In step S38, the determination unit 21 satisfies either (the number of consecutive successful frame transmissions n is equal to the threshold value a) or (the number of frame transmissions t until the MCS is increased is equal to the threshold value g), and (currently It is determined whether or not the condition that the MCS level is not the highest) is satisfied.

  If the determination result in step S38 is affirmative, the process proceeds to step S39. In step S39, the rate determining unit 24 changes the MCS to a level one step higher. In addition, the count unit 22 initializes the frame transmission count t and the frame transmission success count n to 0, and the frame transmission has never been successful after the MCS level is increased by one step. Is changed to True. Thereafter, the process proceeds to step S41.

  On the other hand, when the determination result in step S38 is negative, the process proceeds to step S40. In step S40, the count unit 22 increments the frame transmission count t by 1, and the flag rec is changed to False. Thereafter, the process proceeds to step S41.

  In step S41, the determination unit 21 determines whether or not the number i of the transmitted frame has reached the number of transfer frames nd. If this determination result is negative (the frame number i has reached the number of transfer frames nd), the first adaptive rate control process is terminated.

  On the other hand, if the determination result in step S41 is affirmative (the frame number i has not reached the transfer frame number nd), the process returns to step S32 and the subsequent steps are repeated.

  If it is determined in step S34 that the transmission of the frame transmitted in step S33 has failed, the process proceeds to step S51 in FIG.

  In step S51, the count unit 22 increments the frame transmission count t by 1, increments the frame transmission failure success count m by 1, and initializes the frame transmission success success count n to 0.

  In step S52, the determination unit 21 determines whether or not the flag rec is True. If this determination result is negative (flag rec is False), the process proceeds to step S53. In step S <b> 53, the determination unit 21 determines whether the number of consecutive transmission failures m is 2, 4, 6, 8, or 10. If this determination result is affirmative, the process proceeds to step S54.

In step S54, the threshold value setting unit 23 changes the threshold value a to its initial value a _min and also changes the threshold value g to its initial value g _min . In step S55, the determination unit 21 determines whether or not the current MCS level is not the lowest level.

  If the determination result in step S55 is affirmative (the current MCS level is not the lowest), the process proceeds to step S56. In step S56, the rate determining unit 24 changes the MCS to a level one level lower. If the determination result in step S55 is negative (the current MCS level is the lowest), step S56 is skipped and the process proceeds to step S60.

  Note that the process also proceeds to step S60 if the determination result in step S53 is negative.

  On the other hand, if the determination result in step S52 is affirmative (flag rec is True), the process proceeds to step S57. In step S57, the count unit 22 initializes the frame transmission count t to zero.

In step S <b> 58, the determination unit 21 determines whether or not the number of consecutive transmission failures m is 1. If this determination result is negative (the number m of consecutive transmission failures is not 1), the process proceeds to step S60. On the other hand, if this determination result is affirmative (the number of consecutive transmission failures m is 1), the process proceeds to step S59.

In step S59, the threshold value setting unit 23 changes the threshold value a and the threshold value g. Specifically, a value obtained by multiplying the greater coefficient k ₃ than 1 to threshold value a of the current situation, the maximum value a _max of the threshold a is compared, the threshold a is changed to a value towards their small. Further, a value obtained by multiplying the coefficient k ₂ in the threshold value a of the current situation, and compared the initial value g _min threshold g is, the threshold value g is changed to their greater value. Thereafter, the process proceeds to step S55.

  In step S <b> 60, the determination unit 21 determines whether the number of consecutive transmission failures m is 2 or more. If the determination result is affirmative (the number of consecutive transmission failures m is 2 or more), the process proceeds to step S61. In step S61, the count unit 22 initializes the frame transmission count t to zero. If the determination result in step S60 is negative (the number of consecutive transmission failures m is less than 2), step S61 is skipped. Thereafter, the process returns to step S33 in FIG. 9 and the subsequent steps are repeated.

  In the first adaptive rate control processing described above, in short, immediately after the number of consecutive successful frame transmissions n is greater than or equal to the threshold value a, the MCS is changed to a higher level and the MCS is changed to a higher level. If the frame transmission fails, the MCS is returned to a lower level and the threshold value a is increased, and after the MCS level is increased, the number of consecutive successful frame transmissions n is equal to or greater than the threshold value b. Control is performed to reduce the threshold value a.

According to the first adaptive rate control process, similarly to the ARF process, it is possible to improve the frame transmission success probability without deteriorating the initial pull-in performance of MCS as compared with the ARF process.

  Note that instead of comparing the threshold value with the number n of successful transmissions of frames, a value n ′ calculated based on n may be compared with a threshold value adjusted accordingly.

  FIG. 12 shows a simulation result when the quality of the communication path is improved during the communication by the first adaptive rate control process.

However, in FIG. 12, as in FIG. 5 and FIG. 6, there are six levels from mcs0 to mcs5 in order from the lowest MCS level. Until 120 frames are transmitted, PER is from the bottom to the fourth mcs3. Assume that PER is 1 at mcs4 that is close to 0 and one step higher than that. It is assumed that the quality of the communication channel is improved after 120 frames are transmitted, and PER is close to 0 even for mcs4 and mcs5. Further, the initial value a _min = 10 of the threshold value a, the maximum value a _max = 50, the initial value g _min = 250 of the threshold value g, the coefficient k ₁ = 2, the threshold value b = the initial value a _{min of} the threshold value a, and the coefficient k _1. Set to = 0.

  In the case of the first adaptive rate control process shown in FIG. 12, it is raised to mcs4 when transmitting approximately 155 frames, and is increased to mcs5 when transmitting approximately 165 frames and is stabilized as it is.

  Therefore, according to the first adaptive rate control process, the convergence time until the optimum MCS is converged can be significantly shortened as compared with the case of the AARF process shown in FIG.

<Second Adaptive Rate Control Processing by Adaptive Rate Control Unit 11>
By the way, in the first adaptive rate control process described above, the MCS is determined based on the continuous number of successful frame transmissions and the continuous number of transmission failures. However, the MCS is determined based on the frame transmission failure probability. It may be.

  Next, a second adaptive rate control process for determining the MCS based on the frame transmission failure probability by the adaptive rate control unit 11 will be described.

  FIG. 13 is a flowchart for explaining the second adaptive rate control process. FIG. 14 shows the meanings and initial values of symbols representing thresholds and variables in the flowchart of FIG.

  In step S81, the count unit 22 initializes various variables (initial values are substituted). Various threshold values are initialized by the threshold setting unit 23. In step S <b> 82, the count unit 22 increments the number i assigned to represent the transmission order for the frame transmitted by the transmission unit 12 by one. In step S <b> 83, the count unit 22 increments the frame transmission number l by the transmission unit 12 by one.

  In step S84, the transmission unit 12 transmits the i-th frame. In step S85, the determination unit 21 determines the success or failure of transmission of the i-th frame transmitted in step S84 based on the application rate determination information from the reception unit 13. If it is determined that the transmission is successful, the process proceeds to step S86.

  In step S86, the determination unit 21 causes the number of frames l to be equal to the number of frames f that is a criterion for increasing p, which is the threshold value of the transmission failure rate when increasing the MCS, and the number of frame transmission failures s. It is determined whether or not the value s / l obtained by multiplying the number of frames transmitted by l is smaller than the threshold value c, and the current MCS has just been increased by one level. If this determination result is affirmative, the process proceeds to step S87. On the other hand, if this determination result is negative, step S87 is skipped.

In step S87, the threshold value setting unit 23 changes the threshold value p and the frame number e. Specifically, a value obtained by multiplying the current threshold value p by a coefficient k ₇ is compared with the maximum value p _max of the threshold value p, and the threshold value p is changed to a smaller value thereof. Also, the value obtained by multiplying the current frame number e by the coefficient k ₈ is compared with the minimum value e _min of the frame number e, and the frame number e is changed to the larger value thereof.

  In step S88, the determination unit 21 determines whether or not the number of transmitted frames 1 is different from the number of frames e representing the calculation period of the transmission failure rate r. If this determination result is negative (the number of frames 1 is equal to the number of frames e), the process proceeds to step S89.

  In step S89, the determination unit 21 determines whether or not a value s / l obtained by multiplying the frame transmission failure number s by the frame transmission number l is smaller than the threshold value p, and the current MCS level is not the highest. Determined. If this determination result is affirmative, the process proceeds to step S90. In step S90, the rate determining unit 24 changes the MCS to a level one step higher. Further, the count unit 22 changes the flag rec indicating that the frame transmission has never been successful after the MCS level has been increased by one level to True. Thereafter, the process proceeds to step S92.

  On the other hand, when the determination result in step S89 is negative, the process proceeds to step S91. In step S91, the count rec 22 also changes the flag rec to False. Thereafter, the process proceeds to step S92. In step S92, the count unit 22 initializes the frame transmission failure count s and the number of transmitted frames l to zero.

  In step S93, the determination unit 21 determines whether or not the number i of the transmitted frame has reached the number of transfer frames nd. If this determination result is negative (the frame number i has reached the number of transfer frames nd), the second adaptive rate control process is terminated. If this determination result is negative (the frame number i has not reached the transfer frame number nd), the process returns to step S82 and the subsequent steps are repeated.

  If it is determined in step S85 that the transmission of the i-th frame transmitted in step S84 has failed, the process proceeds to step S94. In step S94, the count unit 22 increments the frame transmission failure count s by one.

  In step S95, the determination unit 21 determines whether the frame transmission failure count s is 1 and the flag rec is True. If this determination result is negative (transmission failure count s is not 1 or flag rec is False), the process proceeds to step S96. In step S96, the determination unit 21 determines whether or not the number of transmitted frames l has reached the threshold value e. If this determination result is affirmative (the number of transmitted frames l has not reached the threshold value e), the process returns to step S83 and the subsequent steps are repeated.

  If the determination result of step S96 is negative (the number of transmitted frames l has reached the threshold value e), the process proceeds to step S97. In step S97, the determination unit 21 determines whether or not a value s / l obtained by multiplying the frame transmission failure number s by the frame transmission number l is greater than a threshold value q. If the determination result is affirmative, the process proceeds to step S99. If the determination result is negative, the process proceeds to step S101.

On the other hand, if the determination result of step S95 is affirmative (the frame transmission failure count s is 1 and the flag rec is True), the process proceeds to step S98. In step S98, the threshold value setting unit 23 changes the threshold value p and the frame number e. Specifically, a value obtained by multiplying the coefficient k ₅ to the threshold p the current is compared minimum value p _min threshold p is the threshold p is changed to their greater value. Further, the value obtained by multiplying the current frame number e by the coefficient k ₆ is compared with the maximum value e _max of the frame number e, and the frame number e is changed to a smaller value thereof.

  In step S99, the determination unit 21 determines whether or not the current MCS level is not the lowest level. If this determination result is affirmative (the current MCS level is not the lowest), the process proceeds to step S100. On the other hand, if the determination result is negative (the current MCS level is the lowest), step S100 is skipped. In step S100, the rate determining unit 24 changes the MCS to a level one step lower. Thereafter, the process proceeds to step S101.

  In step S101, the count unit 22 initializes the frame transmission failure count s and the number of transmitted frames l to 0, and changes the flag rec to False. Thereafter, the process returns to step S83, and the subsequent steps are repeated.

  In the second adaptive rate control process described above, in short, when the frame transmission failure rate r in the predetermined period e (the period in which the frame is transmitted e times) is smaller than the threshold value p, the MCS is raised to one level higher. When the transmission failure rate r is larger than the threshold value q, the MCS is lowered to a level one step lower. Further, when transmission fails immediately after raising MCS to one level higher, threshold p is reduced, and when MCS is raised to one level higher, transmission failure rate r becomes smaller than threshold c. Increases the threshold p. Further, when the threshold value p is reduced, the period e is lengthened, and conversely, when the threshold value p is increased, the period e is shortened.

The transmission failure probability r immediately after raising MCS to one level higher is preferably calculated as a transmission failure probability in a period f (a period in which a frame is transmitted f times) shorter than the period e. The initial value p _max of the threshold value p is preferably set, and the period f is preferably set to the initial value of the period e.

  According to the second adaptive rate control process, similar to the first adaptive rate control process, it is possible to improve the frame transmission success probability without deteriorating the initial pull-in performance of MCS as compared with the ARF process. Can do.

  Instead of comparing the frame transmission failure probability r with a threshold value, a value r ′ calculated based on r may be compared with a threshold value adjusted accordingly.

  By the way, the above-described series of processing can be executed by hardware or can be executed by software. When a series of processing is executed by software, a program constituting the software is installed in the computer. Here, the computer includes, for example, a general-purpose personal computer capable of executing various functions by installing a computer incorporated in dedicated hardware and various programs.

  FIG. 15 is a block diagram illustrating a configuration example of hardware of a computer that executes the above-described series of processing by a program.

  In the computer 200, a CPU (Central Processing Unit) 201, a ROM (Read Only Memory) 202, and a RAM (Random Access Memory) 203 are connected to each other via a bus 204.

  An input / output interface 205 is further connected to the bus 204. An input unit 206, an output unit 207, a storage unit 208, a communication unit 209, and a drive 210 are connected to the input / output interface 205.

  The input unit 206 includes a keyboard, a mouse, a microphone, and the like. The output unit 207 includes a display, a speaker, and the like. The storage unit 208 includes a hard disk, a nonvolatile memory, and the like. The communication unit 209 includes a network interface and the like. The drive 210 drives a removable medium 211 such as a magnetic disk, an optical disk, a magneto-optical disk, or a semiconductor memory.

  In the computer 200 configured as described above, for example, the CPU 201 loads the program stored in the storage unit 208 to the RAM 203 via the input / output interface 205 and the bus 204 and executes the program. A series of processing is performed.

  Note that the program executed by the computer 200 may be a program that is processed in time series in the order described in this specification, or a necessary timing such as when a call is made in parallel. It may be a program in which processing is performed.

  Embodiments of the present disclosure are not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present disclosure.

This indication can also take the following composition.
(1)
An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
A modulation unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and a transmission unit that transmits transmission data obtained as a result in units of frames,
The adaptive rate control unit includes:
When the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n is equal to or greater than a first threshold, the MCS is raised to a high level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, increase the first threshold,
After the MCS is raised to a high level, if the number of successful transmissions n per frame or the value n ′ based on the successful transmission times n is equal to or greater than a second threshold, the first threshold is reduced. apparatus.
(2)
The transmission device according to (1), wherein the second threshold is an initial value of the first threshold.
(3)
The adaptive rate control unit includes:
The transmission apparatus according to (1) or (2), wherein when the transmission in units of frames fails immediately after raising the MCS to a high level, the MCS is lowered to a low level.
(4)
The transmission apparatus according to any one of (1) to (3), wherein the adaptive rate control unit determines success or failure of transmission in units of frames based on an ACK frame transmitted from a reception side.
(5)
An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
In a transmission method of a transmission apparatus comprising: a transmission unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and transmits transmission data obtained as a result of each frame;
By the adaptive rate control unit,
When the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n is equal to or greater than a first threshold, the MCS is raised to a high level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, increase the first threshold,
The step of reducing the first threshold value when the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n becomes equal to or greater than a second threshold after raising the MCS to a high level. Including sending method.
(6)
An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
A program for controlling a transmission apparatus comprising: a transmission unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and transmits transmission data obtained as a result of each frame;
In the adaptive rate control unit,
When the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n is equal to or greater than a first threshold, the MCS is raised to a high level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, increase the first threshold,
The step of reducing the first threshold value when the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n becomes equal to or greater than a second threshold after raising the MCS to a high level. The program which makes the computer of a transmission device perform the process containing this.
(7)
An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
A modulation unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and a transmission unit that transmits transmission data obtained as a result in units of frames,
The adaptive rate control unit includes:
When the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is less than a first threshold, the MCS is raised to a high level,
If the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is greater than or equal to a second threshold, the MCS is lowered to a low level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, the first threshold is reduced,
The transmission apparatus increases the first threshold when the transmission failure probability r or the value r ′ becomes less than a third threshold after raising the MCS to a high level.
(8)
The transmission device according to (7), wherein the third threshold is an initial value of the first threshold.
(9)
The adaptive rate control unit includes:
When reducing the first threshold, the calculation period of the transmission failure probability r is lengthened,
The transmission device according to (7) or (8), wherein the calculation period of the transmission failure probability r is shortened when increasing the first threshold.
(10)
The adaptive rate control unit includes:
The transmission apparatus according to any one of (7) to (9), wherein the calculation period of the transmission failure probability r is shortened after raising the MCS to a high level.
(11)
The adaptive rate control unit includes:
The transmission apparatus according to any one of (7) to (9), wherein the calculation period of the transmission failure probability r is initialized after raising the MCS to a high level.
(12)
An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
In a transmission method of a transmission apparatus comprising: a transmission unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and transmits transmission data obtained as a result of each frame;
By the adaptive rate control unit,
When the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is less than a first threshold, the MCS is raised to a high level,
If the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is greater than or equal to a second threshold, the MCS is lowered to a low level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, the first threshold is reduced,
A transmission method including a step of increasing the first threshold when the transmission failure probability r or the value r ′ is less than a third threshold after raising the MCS to a high level.
(13)
An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
A program for controlling a transmission apparatus comprising: a transmission unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and transmits transmission data obtained as a result of each frame;
In the adaptive rate control unit,
When the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is less than a first threshold, the MCS is raised to a high level,
If the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is greater than or equal to a second threshold, the MCS is lowered to a low level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, the first threshold is reduced,
If the transmission failure probability r or the value r ′ becomes less than a third threshold after raising the MCS to a high level, the computer of the transmission apparatus executes a process including a step of increasing the first threshold Program to make.

  DESCRIPTION OF SYMBOLS 10 Transmission apparatus, 11 Adaptive rate control part, 12 Transmission part, 13 Reception part, 21 Determination part, 22 Count part, 23 Threshold setting part, 24 Rate determination part, 25 Probability calculation part, 200 Computer, 201 CPU

Claims (13)

An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
A modulation unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and a transmission unit that transmits transmission data obtained as a result in units of frames,
The adaptive rate control unit includes:
When the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n is equal to or greater than a first threshold, the MCS is raised to a high level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, increase the first threshold,
After the MCS is raised to a high level, if the number of successful transmissions n per frame or the value n ′ based on the successful transmission times n is equal to or greater than a second threshold, the first threshold is reduced. apparatus. The transmission device according to claim 1, wherein the second threshold is an initial value of the first threshold. The adaptive rate control unit includes:
The transmission apparatus according to claim 2, wherein if transmission in units of frames fails immediately after raising the MCS to a high level, the MCS is lowered to a low level. The transmission apparatus according to claim 2, wherein the adaptive rate control unit determines success or failure of transmission in units of frames based on an ACK frame transmitted from a reception side. An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
In a transmission method of a transmission apparatus comprising: a transmission unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and transmits transmission data obtained as a result of each frame;
By the adaptive rate control unit,
When the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n is equal to or greater than a first threshold, the MCS is raised to a high level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, increase the first threshold,
The step of reducing the first threshold value when the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n becomes equal to or greater than a second threshold after raising the MCS to a high level. Including sending method. An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
A program for controlling a transmission apparatus comprising: a transmission unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and transmits transmission data obtained as a result of each frame;
In the adaptive rate control unit,
When the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n is equal to or greater than a first threshold, the MCS is raised to a high level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, increase the first threshold,
The step of reducing the first threshold value when the number of successful transmissions n in the frame unit or the value n ′ based on the successful transmission number n becomes equal to or greater than a second threshold after raising the MCS to a high level. The program which makes the computer of a transmission device perform the process containing this. An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
A modulation unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and a transmission unit that transmits transmission data obtained as a result in units of frames,
The adaptive rate control unit includes:
When the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is less than a first threshold, the MCS is raised to a high level,
If the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is greater than or equal to a second threshold, the MCS is lowered to a low level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, the first threshold is reduced,
The transmission apparatus increases the first threshold when the transmission failure probability r or the value r ′ becomes less than a third threshold after raising the MCS to a high level. The transmission device according to claim 7, wherein the third threshold is an initial value of the first threshold. The adaptive rate control unit includes:
When reducing the first threshold, the calculation period of the transmission failure probability r is lengthened,
The transmission apparatus according to claim 8, wherein when the first threshold value is increased, a calculation period of the transmission failure probability r is shortened. The adaptive rate control unit includes:
The transmission apparatus according to claim 9, wherein the calculation period of the transmission failure probability r is shortened after raising the MCS to a high level. The adaptive rate control unit includes:
The transmission apparatus according to claim 10, wherein the calculation period of the transmission failure probability r is initialized after raising the MCS to a high level. An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
In a transmission method of a transmission apparatus comprising: a transmission unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and transmits transmission data obtained as a result of each frame;
By the adaptive rate control unit,
When the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is less than a first threshold, the MCS is raised to a high level,
If the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is greater than or equal to a second threshold, the MCS is lowered to a low level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, the first threshold is reduced,
A transmission method including a step of increasing the first threshold when the transmission failure probability r or the value r ′ is less than a third threshold after raising the MCS to a high level. An adaptive rate control unit that controls MCS (Modulation Coding Scheme) applied when transmitting data according to the communication status;
A program for controlling a transmission apparatus comprising: a transmission unit that modulates and encodes the data using the MCS determined by the adaptive rate control unit, and transmits transmission data obtained as a result of each frame;
In the adaptive rate control unit,
When the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is less than a first threshold, the MCS is raised to a high level,
If the transmission failure probability r in units of frames or the value r ′ based on the transmission failure probability r is greater than or equal to a second threshold, the MCS is lowered to a low level,
If the transmission in units of frames fails immediately after raising the MCS to a high level, the first threshold is reduced,
If the transmission failure probability r or the value r ′ becomes less than a third threshold after raising the MCS to a high level, the computer of the transmission apparatus executes a process including a step of increasing the first threshold Program to make.

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