JP2011050042A - Wireless terminal and transmission speed prediction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wireless terminal capable of accurately calculating a predictive transmission speed even in the case where the quantity of communication channels allocated from a wireless base station is dynamically varied. <P>SOLUTION: A wireless terminal 1A is used for a wireless communication system wherein the modulation system of a wireless signal is switched dynamically according to the reception quality of the wireless signal received from a wireless base station. The wireless terminal 1A predicts a reception quality at a future time after the receiving time of the wireless signal, and calculates a predictive transmission speed being the predictive value of a downlink transmission speed at the future time, on the basis of the predicted reception quality. The wireless terminal 1 is provided with a calculation unit 142 which calculates the predictive transmission speed using: a reference transmission speed being the downlink transmission speed determined according to the predicted reception quality; and an allocation ratio which shows a ratio of the downlink communication channel allocated to the wireless terminal within a predetermined period before the receiving time to all the downlink communication channels which can be allocated by the wireless base station within the predetermined period. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a wireless terminal and a transmission rate prediction method for calculating a predicted value of a downlink transmission rate.

  In a wireless communication system, adaptive modulation is known as one of techniques for improving a transmission rate. For example, in downlink communication, the modulation method of the radio signal is dynamically switched according to the reception quality of the radio signal received by the radio terminal from the radio base station. Since the transmission rate changes when the modulation method is switched, it is considered to control the transmission rate and coding rate of the data transmitted by the communication destination device (for example, server or communication terminal) of the wireless terminal according to the downlink transmission rate. Has been.

  Here, when the downlink transmission rate measured by the wireless terminal is transmitted to the communication destination device, a time difference occurs between the measurement time of the downlink transmission rate and the data transmission time in the communication destination device. For this reason, it is preferable that the wireless terminal calculates a predicted transmission rate that is a predicted value of the downlink transmission rate at a future time, and transmits the predicted transmission rate to the communication destination apparatus.

  As a transmission rate prediction method for calculating such a predicted transmission rate, the following method is known (for example, see Patent Document 1). Specifically, the wireless terminal predicts the reception quality at a future time based on the reception quality of the current (and past) wireless signal, and calculates the transmission rate corresponding to the predicted reception quality as the predicted transmission rate. .

Japanese Patent Laying-Open No. 2006-1000093 (paragraphs [0018]-[0028] etc.)

  By the way, the radio base station performs a scheduling process for efficiently assigning a finite communication channel (for example, time slot or frequency) to a plurality of radio terminals. For example, when the number of wireless terminals connected to the wireless base station is large, the communication channels assigned to each wireless terminal by the scheduling process are relatively reduced, so even if the wireless terminal has a good wireless signal reception quality, A high transmission rate may not be obtained.

  However, since the conventional transmission rate prediction method calculates the predicted transmission rate without considering the influence of the scheduling process on the transmission rate, there is a problem that an error is likely to occur in the calculated predicted transmission rate.

  Accordingly, an object of the present invention is to provide a wireless terminal and a transmission rate prediction method capable of accurately calculating a predicted transmission rate even when the amount of communication channels allocated from a radio base station changes dynamically. To do.

  In order to solve the above-described problems, the present invention has the following features. First, the first feature of the present invention is that the radio signal modulation scheme is dynamically switched according to the reception quality of the radio signal received from the radio base station (radio base station 20) via the downlink communication channel. In a communication system, a reception quality at a time later than the reception time of the radio signal is predicted, and a predicted transmission rate that is a predicted value of a downlink transmission rate at the future time is calculated based on the predicted reception quality. A wireless terminal (wireless terminal 1), a reference transmission rate that is a downlink transmission rate determined according to the predicted reception quality, and all of the wireless base stations that can be allocated within a predetermined period before the reception time The predicted transmission rate is calculated using an allocation rate indicating a ratio occupied by the downlink communication channel allocated to the wireless terminal within the predetermined period in the downlink communication channel. That the subject matter in that it comprises a calculation unit (calculation unit 142 or the predicted transmission rate calculating unit 113).

  According to such a feature, since the influence of the scheduling process on the transmission rate is taken into account, even when the amount of communication channels allocated from the radio base station to the radio terminal dynamically changes, the radio terminal Can accurately calculate the predicted transmission rate.

  A second feature of the present invention relates to the first feature of the present invention, wherein the calculation unit calculates an average value or a maximum value of the allocation rate calculated for each predetermined period within a set period longer than the predetermined period. And calculating the multiplication result of the reference transmission rate as the predicted transmission rate.

  A third feature of the present invention relates to the first or second feature of the present invention, and is an index value (for example, DRC or CQI) of reception quality or downlink transmission speed, and a specification of the wireless communication system. A storage unit (storage unit 15A) that stores the defined transmission rate in association with the defined transmission rate, and the calculation unit calculates the defined transmission rate corresponding to the index value according to the predicted reception quality The gist is to obtain from the storage unit, and to calculate the predicted transmission rate using the obtained definition transmission rate as the reference transmission rate.

  The fourth feature of the present invention relates to the first or second feature of the present invention, and corresponds to any index value of reception quality or downlink transmission rate and an average transmission rate based on an actual measurement value of downlink transmission rate. And further storing a storage unit (storage unit 15B), wherein the calculation unit acquires the average transmission rate corresponding to the index value corresponding to the predicted reception quality from the storage unit, and the acquired average The gist is to calculate the predicted transmission rate using the transmission rate as the reference transmission rate.

  A fifth feature of the present invention is according to the fourth feature of the present invention, further comprising an average transmission rate measurement unit (average transmission rate measurement unit 145) for measuring the average transmission rate, wherein the storage unit includes the average transmission rate The gist is to store the average transmission rate measured by the transmission rate measurement unit in association with the index value.

  A sixth feature of the present invention relates to the fourth or fifth feature of the present invention, wherein the storage unit associates the index value with the average transmission rate (average transmission rate table T2) for each reception quality. The calculation unit stores the average transmission rate corresponding to the index value according to the predicted reception quality from the storage unit, out of the association according to the reception quality of the received radio signal. The gist is to obtain and calculate the predicted transmission rate using the obtained average transmission rate as the reference transmission rate.

  A seventh feature of the present invention relates to any one of the first to sixth features of the present invention, and is a measurement unit that measures a round trip delay time between the wireless terminal and a server device that is a communication destination of the wireless terminal. (Round-trip delay time measurement unit 121), reception for controlling the data transmission amount of the server device using the round-trip delay time measured by the measurement unit and the predicted transmission rate calculated by the calculation unit The gist is to further include a determination unit (reception window size determination unit 115) that determines a window size.

  An eighth feature of the present invention relates to the seventh feature of the present invention, wherein the measurement unit measures the round-trip delay time a plurality of times, and the determination unit measures a round-trip delay measured a plurality of times by the measurement unit. The gist is to determine the reception window size using a minimum round-trip delay time of the time and the predicted transmission rate calculated by the calculation unit.

  According to a ninth aspect of the present invention, in the wireless communication system in which the modulation method of the wireless signal is dynamically switched according to the reception quality of the wireless signal received by the wireless terminal from the wireless base station via the downlink communication channel, A transmission rate prediction method for predicting the reception quality at a time later than the reception time of a radio signal and calculating a predicted transmission rate that is a predicted value of a downlink transmission rate at the future time based on the predicted reception quality The reference transmission rate, which is a downlink transmission rate determined according to the predicted reception quality, and the predetermined period in all downlink communication channels that can be allocated by the radio base station within a predetermined period before the reception time. And calculating an estimated transmission rate using an allocation rate indicating a ratio occupied by a downlink communication channel allocated to the wireless terminal in the network. The gist of the Rukoto.

  A tenth feature of the present invention relates to the ninth feature of the present invention, comprising: a step of measuring a round-trip delay time between the wireless terminal and a server device that is a communication destination of the wireless terminal; and the measuring step. The method further comprises: determining a reception window size for controlling the data transmission amount of the server device using the measured round-trip delay time and the predicted transmission rate calculated by the calculating step. And

  ADVANTAGE OF THE INVENTION According to this invention, even if it is a case where the quantity of the communication channel allocated from a wireless base station changes dynamically, the radio | wireless terminal and transmission rate prediction method which can calculate a predicted transmission rate accurately can be provided.

1 is an overall schematic configuration diagram of a wireless communication system according to an embodiment of the present invention. It is a figure which shows an example of the scheduling process of a proportional fairness system. EV-DO REV. It is a figure which shows the definition transmission rate table with which the transmission rate defined by the specification of A and DRC were matched. It is a block diagram which shows the structure of the radio | wireless terminal which concerns on 1st Embodiment of this invention. It is a figure which shows the example of calculation of the allocation rate which concerns on embodiment of this invention. It is a flowchart which shows the processing flow of the prediction transmission rate calculation process which concerns on 1st Embodiment of this invention. It is a flowchart which shows the processing flow of the allocation rate calculation process which concerns on embodiment of this invention. It is a block diagram which shows the structure of the radio | wireless terminal which concerns on 2nd Embodiment of this invention. It is a figure which shows the average transmission rate table with which the average transmission rate based on the measured value of downlink transmission rate, and DRC were matched. It is a flowchart which shows the processing flow of the prediction transmission rate calculation process which concerns on 2nd Embodiment of this invention. It is a figure which shows the average transmission-rate table which concerns on 3rd Embodiment of this invention. It is a flowchart which shows the process flow of the estimated transmission rate calculation process which concerns on 3rd Embodiment of this invention. It is a block diagram which shows the structural example at the time of applying the radio | wireless terminal which concerns on 1st Embodiment of this invention to an OFDMA system. It is a flowchart which shows the processing flow of the allocation rate calculation process in an OFDMA system. It is a whole schematic block diagram of the radio | wireless communications system which concerns on 4th Embodiment of this invention. It is a figure which shows the structure of the radio | wireless terminal which concerns on 4th Embodiment of this invention. It is a figure which shows the structural example of the multidimensional table which concerns on 4th Embodiment of this invention. It is a graph which shows the relationship between a receiving window size, a transmission rate, and a round-trip delay time in a certain wireless communication environment in CDMA 1x EV-DO. It is a flowchart which shows operation | movement of the TCP process part which concerns on 4th Embodiment of this invention. It is a flowchart which shows operation | movement of the device driver part which concerns on 4th Embodiment of this invention.

  Next, an embodiment of the present invention will be described with reference to the drawings. In the description of the drawings in the following embodiments, the same or similar parts are denoted by the same or similar reference numerals.

(1) Overview of Radio Communication System FIG. 1 is an overall schematic configuration diagram of a communication system including a radio terminal 1 according to the first to third embodiments.

  As illustrated in FIG. 1, the wireless terminal 1 performs wireless communication with the wireless base station 20 and also performs communication with the communication destination device 40 via the wireless base station 20 and the communication network 30. The communication destination device 40 is, for example, a server or a communication terminal. In FIG. 1, there is one wireless terminal 1 that performs wireless communication with the wireless base station 20, but a plurality of wireless terminals 1, 2,... Perform wireless communication with the wireless base station 20. And

  In the first to third embodiments, the wireless communication between the wireless terminals 1, 2,... And the wireless base station 20 is performed by cdma2000 nx evolution-data only (EV The communication in the downstream direction (called “forward link” in EV-DO) will be mainly described.

  The radio terminal 1 measures the reception quality of the radio signal received from the radio base station 20 (specifically, the signal-to-interference noise ratio (SINR) or carrier-to-interference wave ratio (CIR) of the pilot signal). The wireless terminal 1 predicts the reception quality at a future time (that is, the next frame) from the measured variation tendency of the reception quality. The radio terminal 1 transmits data rate control (DRC), which is an index value of “maximum transmission rate that can be received at a predetermined error rate or less” expected from the predicted reception quality (hereinafter, “predicted reception quality”) to the radio base station 20. Send to. The radio base station 20 receives DRCs from the radio terminals 1, 2,.

  The radio base station 20 assigns communication channels to the radio terminals 1, 2,... And performs radio communication with the radio terminals 1, 2,. In EV-DO, frequency resources are divided into time units called slots (for example, 1/600 second), and the slots are assigned to the wireless terminals 1, 2,... As communication channels. The radio base station 20 transmits a radio signal to the radio terminal 1 in the downlink slot assigned to the radio terminal 1.

  The radio base station 20 performs a scheduling process for efficiently allocating downlink slots to the radio terminals 1, 2,... Based on the DRC received from the radio terminals 1, 2,. A method called proportional fairness is used for the scheduling process. Specifically, for each of the wireless terminals 1, 2,..., The wireless base station 20 transmits the data amount R transmitted during the past fixed slot (for example, 1000 slots) (for example, 1.67 seconds), the wireless terminals 1, 2,. DRC / R is calculated from the DRC received from 2,..., And a downlink slot is assigned to the wireless terminal having the largest DRC / R value.

  FIG. 2 is a diagram illustrating an example of a proportional fairness type scheduling process. In the example of FIG. 2, since the wireless terminal 4 with good reception quality and a large amount of data to be received from the wireless base station 20 has entered the communication area of the wireless base station 20, Downlink slots 8 are continuously assigned to the wireless terminals 4. After downlink slot 8, downlink slots are alternately assigned to radio terminals 1 to 4 every four slots.

  The radio base station 20 performs adaptive modulation processing for switching the modulation scheme of the downlink radio signal based on the DRC received from the radio terminals 1, 2,. In adaptive modulation, a plurality of modulation schemes (also called modulation classes) are defined in accordance with the combination of the modulation multi-level number and the coding rate. When the reception quality of the radio signal received by the radio terminal 1 from the radio base station 20 is high, the radio base station 20 selects a high-speed modulation method with low error tolerance and the reception quality is low. For this, a low-speed modulation scheme with high error tolerance is selected.

  FIG. 3 shows EV-DO REV. It is a figure which shows the defined transmission rate table T1 with which the transmission rate (henceforth a definition transmission rate) defined by the specification of A and DRC were matched. In the example of FIG. 3, there are DRCs 1 to 14, and each DRC is associated with a different defined transmission rate. The wireless terminal 1 transmits the DRC to the wireless base station 20 to specify the transmission rate of data transmitted by the wireless base station 20. However, if sufficient downlink slots are not allocated to the wireless terminal 1 as a result of the scheduling process described above, the defined transmission rate specified by the DRC is not provided.

  The wireless terminal 1 calculates a predicted transmission rate that is a predicted value of the downlink transmission rate in the next frame based on the predicted reception quality. The wireless terminal 1 transmits the calculated predicted transmission rate to the communication destination device 40 via the wireless base station 20 and the communication network 30. The wireless base station 20 and the communication destination device 40 control the transmission rate of data to be transmitted to the wireless terminal 1 in accordance with the predicted transmission rate transmitted from the wireless terminal 1.

(2) 1st Embodiment Next, 1st Embodiment of the radio | wireless terminal of this invention is described. Specifically, (2.1) Configuration of the wireless terminal according to the first embodiment, (2.2) Operation of the wireless terminal according to the first embodiment, (2.3) Effects of the first embodiment will be described. To do.

(2.1) Configuration of Radio Terminal According to First Embodiment FIG. 4 is a block diagram showing the configuration of the radio terminal 1A. The configuration of the wireless terminal 1A will be described in the order of (2.1.1) schematic configuration, (2.1.2) control unit and storage unit configuration.

(2.1.1) Schematic Configuration As shown in FIG. 4, the wireless terminal 1A includes an antenna 11, a wireless unit 12, a signal processing unit 13, a control unit 14A, a storage unit 15A, an audio input / output unit 16, and video input / output. Unit 17, operation receiving unit 18, and battery 19.

  The wireless unit 12 transmits and receives wireless signals via the antenna 11. The radio unit 12 converts the radio signal and the baseband signal and inputs / outputs the baseband signal to / from the signal processing unit 13.

  The signal processing unit 13 demodulates and decodes a received signal (received baseband signal) and modulates and encodes a transmitted signal (transmitted baseband signal).

  The control unit 14A is configured using, for example, a CPU, and controls various functions provided in the wireless terminal 1A.

  The storage unit 15A is configured using, for example, a memory, and stores various types of information used for control in the control unit 14A.

  The voice input / output unit 16 includes a microphone that inputs a voice signal to the control unit 14A based on the collected voice, and a speaker that outputs a voice based on the voice signal from the control unit 14A.

  The video input / output unit 17 includes a display that outputs characters and video, and a camera that inputs a video signal obtained by photographing a subject to the control unit 14A.

  The operation receiving unit 18 is configured using a numeric keypad, function keys, a touch panel, or the like, and receives an operation from a user.

  The battery 19 stores power to be supplied to the wireless unit 12, the signal processing unit 13, the control unit 14 </ b> A, the storage unit 15 </ b> A, the audio input / output unit 16, the video input / output unit 17, and the operation receiving unit 18.

(2.1.2) Configuration of Control Unit and Storage Unit Next, the configuration of the control unit 14A and the storage unit 15A will be described.

  The control unit 14A includes a reception quality measurement unit 140, a DRC acquisition unit 141, a calculation unit 142, and an application processing unit 143. The application processing unit 143 processes an application such as a VoIP (Voice over Internet Protocol) application or a video streaming application.

  The calculation unit 142 includes an allocation rate calculation unit 142a and a predicted transmission rate calculation unit 142b. The storage unit 15A includes a DRC storage unit 151, a definition transmission rate storage unit 152A, and an allocation rate storage unit 153.

  The DRC storage unit 151 stores a DRC table in which reception quality (SINR or CIR) and DRC are associated with each other. In the DRC table, one DRC is associated with a predetermined range of reception quality.

  The reception quality measuring unit 140 measures the reception quality of the radio signal received from the radio base station 20 periodically (for example, every frame or every slot).

  The DRC acquisition unit 141 calculates a predicted reception quality based on the current and past reception quality measured by the reception quality measurement unit 140, and acquires a DRC corresponding to the calculated predicted reception quality from the DRC storage unit 151. For the calculation of the predicted reception quality, for example, a calculation method such as linear prediction is used.

  The allocation rate calculation unit 142a calculates an allocation rate indicating the ratio of the downlink slots allocated to the radio terminal 1 within the predetermined period in all the downlink slots that can be allocated by the radio base station 20 within the predetermined period in the past. To do.

  FIG. 5 is a diagram illustrating a calculation example of the allocation rate. In the example of FIG. 5, downlink slots 1 and 5 are allocated to the wireless terminal 1, downlink slots 2, 3, and 7 are allocated to the wireless terminal 2, and downlink slots 4, 8, and 9 are allocated to the wireless terminal 3. . When the predetermined period is the period of the downlink slots 1 to 9, the allocation rate for the wireless terminal 1 is 33.3%.

  The allocation rate calculation unit 142a calculates the allocation rate for each predetermined period. The allocation rate calculation unit 142a stores, in the allocation rate storage unit 153, an average value (or maximum value) of the allocation rates calculated within a set period longer than the predetermined period (9 slot period in the example of FIG. 5). Let The set period is, for example, about five times the predetermined period. The allocation rate calculation unit 142a stores the average value of the allocation rate in the allocation rate storage unit 153 or sets the maximum value of the allocation rate to the allocation rate storage unit 153 according to the type of application processed by the application processing unit 143. You may select whether to memorize.

  For example, when the “average value” of the allocation rate is used, the average transmission speed (data rate) can be predicted, and data (voice data, etc.) that gives priority to stable transmission such as data that requires a certain amount of bandwidth guarantee ) Suitable for transmission. When the “maximum value” of the allocation rate is used, the maximum transmission capability of the transmission path can be predicted, and it is suitable for data (such as downloading a file by FTP) where high speed transmission is desirable even if it is somewhat unstable.

  The predicted transmission rate calculation unit 142b calculates the predicted transmission rate in response to a request from the application processing unit 143. The predicted transmission rate calculation unit 142b multiplies the reference transmission rate, which is a downlink transmission rate determined according to the predicted reception quality, and the average value (or maximum value) of the allocation rate stored in the allocation rate storage unit 153. Is calculated as the predicted transmission rate.

  In the first embodiment, the predicted transmission rate calculation unit 142b uses the definition transmission rate stored in the definition transmission rate storage unit 152A as the reference transmission rate. Specifically, the predicted transmission rate calculation unit 142b acquires the definition transmission rate corresponding to the DRC of the latest section acquired by the DRC acquisition unit 141 from the definition transmission rate storage unit 152A, and assigns the acquired definition transmission rate and the allocation The multiplication result with the average value (or maximum value) of the allocation rate stored in the rate storage unit 153 is calculated as the predicted transmission rate. The predicted transmission rate calculated by the predicted transmission rate calculation unit 142b is transmitted from the application processing unit 143 to the communication destination device 40.

(2.2) Operation of Wireless Terminal According to First Embodiment Next, the operation of the wireless terminal 1 will be described in the order of (2.2.1) general operation and (2.2.2) allocation rate calculation operation. .

(2.2.1) Schematic Operation FIG. 6 is a flowchart showing a processing flow of predicted transmission rate calculation processing according to the first embodiment. The processing flow shown in FIG. 6 is executed when a predicted transmission rate calculation request is received from the application processing unit 143 or at predetermined time intervals.

  In step S101, the DRC acquisition unit 141 acquires the DRC corresponding to the predicted reception quality from the DRC storage unit 151.

  In step S102, the predicted transmission rate calculation unit 142b acquires the definition transmission rate corresponding to the DRC acquired by the DRC acquisition unit 141 from the definition transmission rate storage unit 152A.

  In step S103, the predicted transmission rate calculation unit 142b acquires an average value (or maximum value) of the allocation rate from the allocation rate storage unit 153.

  In step S104, the predicted transmission rate calculation unit 142b predicts the multiplication result of the definition transmission rate acquired from the definition transmission rate storage unit 152A and the average value (or maximum value) of the allocation rate acquired from the allocation rate storage unit 153. Calculate as transmission rate.

(2.2.2) Allocation Rate Calculation Operation FIG. 7 is a flowchart showing the processing flow of the allocation rate calculation process.

  In steps S111 to S113, the allocation rate calculation unit 142a counts the number of downlink slots allocated from the radio base station 20 within a predetermined period.

  In step S114, the allocation rate calculation unit 142a calculates the allocation rate within the predetermined period based on the counted number of downlink slots.

  In step S115, the allocation rate calculation unit 142a calculates an average value (or maximum value) of the allocation rates calculated every predetermined period. The allocation rate storage unit 153 stores the average value (or maximum value) calculated by the allocation rate calculation unit 142a.

  In steps S116 to S118, the allocation rate calculation unit 142a waits for a predetermined time until the calculation of the allocation rate within the next predetermined period starts, and after the predetermined time has elapsed, the allocation rate within the next predetermined period in step S111. Start calculating.

  Instead of the timers in steps S116 to S118, the allocation rate calculation process (steps S111 to S115) may be performed by a command or a function.

(2.3) Effects of the First Embodiment According to the first embodiment, not only the defined transmission rate defined in the EV-DO specification but also the predicted transmission in consideration of the scheduling process status of the radio base station 20 Since the rate is calculated, the predicted transmission rate can be calculated with high accuracy even when the amount of downlink slots allocated from the radio base station 20 to the radio terminal 1A changes dynamically.

(3) Second Embodiment Next, a second embodiment of the wireless terminal of the present invention will be described. In the first embodiment, the defined transmission rate is used as the reference transmission rate, but in the second embodiment, the average transmission rate based on the actually measured value of the downlink transmission rate is used as the reference transmission rate.

  Hereinafter, (3.1) Configuration of the wireless terminal according to the second embodiment, (3.2) Operation of the wireless terminal according to the second embodiment, and (3.3) Effects of the second embodiment will be described. However, a different point from 1st Embodiment is demonstrated and the overlapping description is abbreviate | omitted.

(3.1) Configuration of Radio Terminal According to Second Embodiment FIG. 8 is a block diagram showing the configuration of the radio terminal 1B according to the second embodiment.

  As illustrated in FIG. 8, the control unit 14B of the wireless terminal 1B includes an average transmission rate measurement unit 145 and a table management unit 146.

  The average transmission rate measurement unit 145 measures an average transmission rate that is an average value of downlink transmission rates. Specifically, the average transmission rate measurement unit 145 measures the downlink transmission rate for each DRC in a certain period, and considers the average value of the measured downlink transmission rate in consideration of HARQ using the number of transmissions and the reception success probability. Average transmission speed.

  Specifically, average transmission rate measurement section 145 first counts the number of HARQ retransmissions for each DRC. For example, in DRC “5”, the maximum number of HARQ transmissions (the number of retransmissions) is specified as four. Here, DRC “5” is a transmission rate defined in the specification of 307.2 kbps, which is a value when four retransmissions are used up. However, in actuality, even with DRC “5”, decoding may succeed in 1 to 3 retransmissions, and decoding may fail in 4 retransmissions. Therefore, in the second embodiment, a value closer to the actual transmission rate is obtained using the probability distribution of the number of HARQ transmissions for each DRC from the radio information. Therefore, for each DRC, the number of receptions at which the decoding is successful is counted, and the probability distribution is periodically updated. The average transmission rate is calculated by the following formula.

In Equation (1), S _DRC is the average transmission rate, N _DRC is the maximum number of slots (maximum number of transmissions), T _DRC is the transmission rate defined in the specification, and P _DRCn is the nth transmission. This is the probability of correct decoding by (retransmission).

  For example, the correspondence relationship between the number of HARQ transmissions of DRC “5” and the decoding success probability obtained from the wireless information is the first “4%”, the second “15%”, the third “50%”, the fourth Assume that “30%” and error “1%”. In this case, the average transmission rate is 438.28 kbps from Equation (1).

  The table management unit 146 creates an average transmission rate table T2 in which the DRC acquired by the DRC acquisition unit 141 is associated with the average transmission rate measured by the average transmission rate measurement unit 145, and the created average transmission rate table T2 is stored in the average transmission rate storage unit 152B of the storage unit 15B. As a result, the average transmission rate storage unit 152B stores an average transmission rate table T2 in which DRCs and average transmission rates are associated with each other, as shown in FIG.

(3.2) Operation of Radio Terminal According to Second Embodiment FIG. 10 is a flowchart showing a process flow of a predicted transmission rate calculation process according to the second embodiment.

  In step S201, the DRC acquisition unit 141 acquires the DRC corresponding to the predicted reception quality from the DRC storage unit 151.

  In step S202, the predicted transmission rate calculation unit 142b acquires the average transmission rate corresponding to the DRC acquired by the DRC acquisition unit 141 from the average transmission rate storage unit 152B.

  In step S203, the predicted transmission rate calculation unit 142b acquires an average value (or maximum value) of the allocation rate from the allocation rate storage unit 153.

  In step S204, the predicted transmission rate calculation unit 142b uses the multiplication result of the average transmission rate acquired from the average transmission rate storage unit 152B and the average value (or maximum value) acquired from the allocation rate storage unit 153 as the predicted transmission rate. calculate.

(3.3) Effect of Second Embodiment According to the second embodiment, instead of the defined transmission rate defined in the EV-DO specification, the average transmission rate based on the actual measured value of the downlink transmission rate is used. Thus, since the predicted transmission rate is calculated based on the reference transmission rate adapted to the actual usage environment of the wireless terminal 1B, the predicted transmission rate can be calculated with higher accuracy.

(4) Third Embodiment Next, a third embodiment of the wireless terminal of the present invention will be described. In the second embodiment described above, only one average transmission rate table T2 is used. However, in the third embodiment, an average transmission rate table T2 for each reception quality range is used.

  Hereinafter, (4.1) Configuration of the wireless terminal according to the third embodiment, (4.2) Operation of the wireless terminal according to the third embodiment, and (4.3) Effects of the third embodiment will be described. However, a different point from 1st Embodiment and 2nd Embodiment is demonstrated, and the overlapping description is abbreviate | omitted.

(4.1) Configuration of Radio Terminal According to Third Embodiment A radio terminal according to the third embodiment is configured similarly to the radio terminal 1B according to the second embodiment, but is stored in the average transmission rate storage unit 152B. The configuration of the average transmission rate table T2 is different from that of the second embodiment. In the third embodiment, the average transmission rate storage unit 152B, as shown in FIG. 11, sets the average transmission rate tables T2a, T2b, and T2c for each range of reception quality (SINR in the example of FIG. 11) as DRC, average transmission rate, and Are stored in the average transmission rate table T2.

  In the example of FIG. 11, the average transmission rate table T2a used when the SINR measured by the reception quality measurement unit 140 is −12 dB to −10 dB, and the average transmission used when the SINR is −10 dB to −8 dB. A speed table T2b and an average transmission speed table T2c used when the SINR is −8 dB to −6 dB are created.

  A procedure for creating such average transmission rate tables T2a, T2b, and T2c will be described. The average transmission rate measurement unit 145 measures the average transmission rate in the same manner as in the second embodiment. The table management unit 146 associates the DRC acquired by the DRC acquisition unit 141, the average transmission rate measured by the average transmission rate measurement unit 145, and the reception quality measured by the reception quality measurement unit 140 with an average transmission. The speed tables T2a, T2b, and T2c are created, and the created average transmission speed tables T2a, T2b, and T2c are stored in the average transmission speed storage unit 152B.

  In the above-described embodiment, there may be a case where a plurality of tables are involved (for example, SINR = −10 dB). In this case, the design may be made so that any one of the tables is involved.

(4.2) Operation of Radio Terminal According to Third Embodiment FIG. 12 is a flowchart showing a processing flow of predicted transmission rate calculation processing according to the third embodiment.

  In step S301, the DRC acquisition unit 141 acquires the DRC corresponding to the predicted reception quality from the DRC storage unit 151.

  In step S302, the reception quality measuring unit 140 measures the reception quality of the reception signal from the radio base station 20.

  In step S303, the predicted transmission rate calculation unit 142b acquires the average transmission rate corresponding to the DRC acquired by the DRC acquisition unit 141 and the reception quality measured by the reception quality measurement unit 140 from the average transmission rate storage unit 152B. To do. Specifically, the predicted transmission rate calculation unit 142b identifies and identifies a measured transmission rate table corresponding to the reception quality measured by the reception quality measurement unit 140 from the average transmission rate tables T2a, T2b, and T2c. In the measured transmission rate table, the average transmission rate corresponding to the DRC acquired by the DRC acquisition unit 141 is acquired.

  In step S304, the predicted transmission rate calculation unit 142b acquires the average value (or maximum value) of the allocation rate from the allocation rate storage unit 153.

  In step S305, the predicted transmission rate calculation unit 142b uses the multiplication result of the average transmission rate acquired from the average transmission rate storage unit 152B and the average value (or maximum value) acquired from the allocation rate storage unit 153 as the predicted transmission rate. calculate.

(4.3) Effects of Third Embodiment According to the third embodiment, the following effects can be obtained in addition to the effects described in the second embodiment. Specifically, a reference transmission rate (average transmission rate) appropriate for the current reception quality can be used for calculation of the predicted transmission rate, and the predicted transmission rate can be calculated with higher accuracy.

(5) Modification Example of First Embodiment to Third Embodiment (5.1) Modification Example of Allocation Rate Calculation Subject In the first to third embodiments described above, the allocation rate calculation unit 142a of the wireless terminal 1 Calculated the average value or maximum value of the allocation rate, but the radio base station 20 calculates the average value or maximum value, and transmits the calculated average value or maximum value from the radio base station 20 to the radio terminal 1. May be.

  According to such a configuration, although the overhead is increased as compared with the first to third embodiments, the allocation rate calculation unit 142a of the wireless terminal 1 can be made unnecessary, so the processing load on the wireless terminal 1 is reduced. Can be reduced.

(5.2) Application Example to OFDMA System In the above-described first to third embodiments, the EV-DO wireless communication system has been described. However, the present invention is not limited to the EV-DO system, and is not limited to the OFDMA (Orthogonal Frequency Division). The present invention can be applied to a wireless communication system (hereinafter referred to as an OFDMA system) employing multiple access.

  Examples of such an OFDMA system include LTE (Long Term Evolution) standardized in 3GPP (3rd Generation Partnership Project), WiMAX standardized in IEEE 802.16, and the like.

  In these OFDMA systems, a DRC is not transmitted from the radio terminal 1 to the radio base station 20, but a CQI (Channel Quality Indicator) that is an index value of the reception quality of the radio signal received by the radio terminal 1 is used. To the radio base station 20.

  The embodiment described above can be modified as follows to be applied to an OFDMA system. FIG. 13 is a block diagram of the wireless terminal 1C when the first embodiment is applied to an OFDMA system.

  The CQI storage unit 151C illustrated in FIG. 13 stores a CQI table in which reception quality is associated with CQI. The definition transmission rate storage unit 152C stores a definition transmission rate table in which CQIs are associated with definition transmission rates. The CQI acquisition unit 141C calculates the predicted reception quality, and acquires the CQI corresponding to the calculated predicted reception quality from the CQI storage unit 151C.

  As shown in FIG. 14, the allocation rate calculation unit 142a, for example, downloads assigned to the radio terminal 1D in all downlink communication channels (T × F) that can be assigned by the radio base station 20 within one frame (predetermined period). An allocation rate indicating a ratio occupied by the communication channel (T1 × F1) is calculated. In the OFDMA system, a downlink communication channel is configured by a combination of a frequency (subchannel) and a time slot, and the downlink communication channel is called a resource block (RB) in LTE. The allocation rate calculation unit 142a stores the average value (or maximum value) of the allocation rate in the allocation rate storage unit 153.

  The predicted transmission rate calculation unit 142b acquires the definition transmission rate corresponding to the CQI acquired by the CQI acquisition unit 141C from the definition transmission rate storage unit 152A, and calculates the average value (or maximum value) of the allocation rate from the allocation rate storage unit 153. Obtained, and the multiplication result of the obtained defined transmission rate and the obtained average value (or maximum value) is calculated as the predicted transmission rate. Other configurations are the same as those of the first embodiment. Similarly, the second and third embodiments described above can be applied to an OFDMA system.

(5.3) Modification Example of Second Embodiment and Third Embodiment In the second embodiment and the third embodiment described above, the average transmission rate table T2 is created in the wireless terminal 1B. The average transmission rate table T2 may be stored in the wireless terminal 1B before shipment.

  That is, an average transmission rate table T2 created empirically or experimentally may be stored in advance in the wireless terminal 1B, and the average transmission rate table T2 may not be updated by the wireless terminal 1B.

  According to such an embodiment, although the environment adaptation capability is lower than in the second embodiment and the third embodiment, the processing load of the wireless terminal 1B can be reduced as compared with the second embodiment and the third embodiment.

(5.4) Modification Example of Wireless Terminal In the first to third embodiments described above, a mobile phone terminal is exemplified as the wireless terminal 1, but not limited to a mobile phone terminal, a card-type wireless terminal or It may be a terminal on which a wireless communication device is mounted.

(6) Fourth Embodiment Next, a fourth embodiment will be described. The fourth embodiment is an embodiment for determining a TCP (Transmission Control Protocol) reception window size using the predicted transmission rate calculated by the predicted transmission rate calculation processing according to the first to third embodiments. .

  In a high-speed and large-capacity wireless communication system, many applications using TCP are used for the transport layer of the OSI reference model.

  As illustrated in FIG. 15, in TCP, the server apparatus 400 transmits data, the wireless terminal 1 as a client receives the data and transmits an acknowledgment (ACK), and the server apparatus 400 receives ACK. The server device 400 is, for example, a mail server or a content server.

  In TCP, the reception window size is set as an amount by which the server apparatus 400 can continuously transmit data to the wireless terminal 1 without receiving an ACK. The wireless terminal 1 determines the reception window size and adjusts the data transmission amount from the server device 400 by including information indicating the reception window size in the ACK transmitted to the server device 400.

  If the reception window size is too small, the bandwidth of the transmission path cannot be used to the maximum, and the TCP transmission speed reaches its peak. On the other hand, if the reception window size is too large, the amount of data that can be sent at once on the transmission path will be exceeded. In this case, the data that could not be sent is temporarily stored in the buffer of the router, for example, but the arrival time of each packet is delayed correspondingly, and the TCP transmission rate is lowered. Further, when a packet overflows from the buffer of the router, a packet loss occurs, so that the TCP transmission speed decreases.

  From the above, unless the reception window size is set to an appropriate value, the transmission speed of TCP decreases, and the communication performance of applications using TCP deteriorates.

  The reception window size is ideally set to the value obtained by the following equation (2) (W. Richard Stevens, “Detailed TCP / IP <Vol.1> Protocol”, Pearson Education (pp. 327, 2000)).

  Reception window size (bit) = Transmission speed (bit / sec) x Round-trip delay time (sec) (2)

  The round-trip delay time in equation (2) is a delay that occurs only in the link portion between nodes, excluding the queue wait delay in the nodes (routers and the like) on the communication path.

(6.1) Configuration of Radio Terminal According to Fourth Embodiment FIG. 16 is a diagram illustrating a configuration of the radio terminal 1 according to the fourth embodiment.

  As shown in FIG. 16, the wireless terminal 1 according to the fourth embodiment includes a physical layer processing unit P1, a data link layer processing unit P2, a network layer processing unit P3, a transport layer processing unit P4, a session layer processing unit P5, It has a presentation layer processing unit P6 and an application layer processing unit P7. The physical layer processing unit P1, data link layer processing unit P2, network layer processing unit P3, transport layer processing unit P4, session layer processing unit P5, presentation layer processing unit P6, and application layer processing unit P7 are OSI reference models. These correspond to the physical layer, data link layer, network layer, transport layer, session layer, presentation layer, and application layer, respectively.

  Part of the physical layer processing unit P1 and the data link layer processing unit P2 corresponds to the radio unit 12 and the signal processing unit 13 according to the first to third embodiments. A part of the data link layer processing unit P2, the network layer processing unit P3, the transport layer processing unit P4, the session layer processing unit P5, the presentation layer processing unit P6, and the application layer processing unit P7 are the first to third embodiments. It corresponds to the control unit 14 according to the embodiment.

  The transport layer processing unit P4 includes a TCP processing unit 120 that performs processing according to TCP. The data link layer processing unit P2 includes a device driver unit 110. The device driver unit 110 functions as an interface between the OS of the wireless terminal 1 and the wireless communication devices (the wireless unit 12 and the signal processing unit 13) and controls the wireless communication device.

(6.1.1) Configuration of TCP Processing Unit Next, the configuration of the TCP processing unit 120 will be described. As shown in FIG. 16, the TCP processing unit 120 includes a round-trip delay time measurement unit 121, a minimum round-trip delay time storage unit 122, a minimum round-trip delay time notification unit 123, a reception window size acquisition unit 124, a reception window size adjustment unit 125, And an ACK generation unit 126.

  The round-trip delay time measurement unit 121 periodically calculates the round-trip delay time between the wireless terminal 1 and the server apparatus 400 based on the segment received from the server apparatus 400 using a method such as a TCP timestamp option. taking measurement. A segment is a minimum unit of data handled by TCP. An IP packet is constructed by adding an IP header to a segment.

  The minimum round-trip delay time storage unit 122 stores the minimum value of the round-trip delay time measured by the round-trip delay time measurement unit 121 as the minimum round-trip delay time. It is preferable that the minimum round-trip delay time storage unit 122 periodically updates the stored minimum round-trip delay time.

  The reason for using the minimum round trip delay time is as follows. In order to obtain the optimum reception window size, it is preferable to use a delay that occurs only in the link portion, excluding the queue waiting delay, as the round-trip delay time value. The delay of the link portion never becomes zero, but the queue waiting delay becomes a value close to zero when the queue of the router on the way is almost empty. Therefore, the minimum round-trip delay time is regarded as a round-trip delay time composed of the delay of only the link portion excluding the queue wait delay.

  The minimum round trip delay time notification unit 123 periodically notifies the device driver unit 110 of the minimum round trip delay time stored in the minimum round trip delay time storage unit 122. The time interval for notifying the device driver unit 110 of the minimum round-trip delay time is determined to be n seconds in advance, for example, in the TCP setting.

  The device driver unit 110 notified of the minimum round-trip delay time determines the reception window size based on the minimum round-trip delay time. Details of the method of determining the reception window size will be described later.

  In the device driver unit 110, for example, a means for calculating the reception window size is implemented as an API (Application Program Interface). The minimum round-trip delay time notification unit 123 passes the minimum round-trip delay time to the API of the device driver unit 110. The API determines the reception window size, and returns the determined reception window size to the TCP processing unit 120 as a return value.

  The reception window size acquisition unit 124 acquires the reception window size notified from the device driver unit 110.

  The reception window size adjustment unit 125 compares the reception window size acquired by the reception window size acquisition unit 124 with the current free space of the reception buffer, and adjusts the reception window size according to the comparison result. The reception buffer is provided in the storage unit 15 described in the first to third embodiments.

  The ACK generation unit 126 generates an ACK segment to be transmitted to the server device 400. The ACK segment includes information indicating the reception window size adjusted by the reception window size adjustment unit 125. The ACK segment generated by the ACK generation unit 126 is transmitted to the server device 400 via the network layer processing unit P3, the data link layer processing unit P2, and the physical layer processing unit P1.

(6.1.2) Configuration of Device Driver Unit Next, the configuration of the device driver unit 110 will be described. The device driver unit 110 is calculated by the multidimensional table T (see FIG. 17), the round-trip delay time notified from the TCP processing unit 120, and the predicted transmission rate calculation processing according to the first to third embodiments. The reception window size is determined from the predicted transmission rate.

  As shown in FIG. 16, the device driver unit 110 includes a minimum round-trip delay time acquisition unit 111, a wireless communication information acquisition unit 112, a predicted transmission rate calculation unit 113, a multidimensional table storage unit 114, a reception window size determination unit 115, and A reception window size notification unit 116 is provided.

  The minimum round-trip delay time acquisition unit 111 acquires the minimum round-trip delay time notified from the TCP processing unit 120.

  The wireless communication information acquisition unit 112 acquires wireless communication information related to the state of wireless communication. The wireless communication information is information used for predictive transmission rate calculation processing according to the first to third embodiments. For example, DRC (Data Rate Control), MCS (Modulation and Coding Scheme) level, SINR (Signal -to-Interference and Noise power Ratio), RSSI (Received Signal Strength Indicator), scheduling information of the radio base station 20, and the like correspond to radio communication information. The DRC is information indicating the transmission quality corresponding to the radio quality predicted in the next frame. The MCS level is information indicating a combination of a modulation scheme and a coding scheme applied to wireless communication. The DRC and MCS levels indicate the transmission quality corresponding to the radio quality. For example, in CDMA 1x EV-DO Rev. A, the transmission rate in the wireless section varies between 38.4 kbps and 3072 kbps depending on the wireless state at that time. SINR and RSSI are index values representing radio quality (goodness of received signal). The scheduling information is information indicating how many radio communication resources are allocated to the terminal itself.

  The predicted transmission rate calculation unit 113 executes the predicted transmission rate calculation processing according to the first to third embodiments using the wireless communication information acquired by the wireless communication information acquisition unit 112, and calculates the predicted transmission rate. To do.

  The multidimensional table storage unit 114 stores in advance a multidimensional table T in which the round trip delay time, the predicted transmission rate, and the reception window size are associated with each other. The multidimensional table T includes values of reception window sizes obtained by experiments or simulations. Details of the multidimensional table T will be described later.

  The reception window size determination unit 115 refers to the multi-dimensional table storage unit 114, and receives reception corresponding to the minimum round-trip delay time notified from the TCP processing unit 120 and the predicted transmission rate calculated by the predicted transmission rate calculation unit 113. Determine the window size.

  The reception window size notification unit 116 notifies the TCP processing unit 120 of the reception window size determined by the reception window size determination unit 115.

(6.2) Multidimensional Table Next, the configuration of the multidimensional table T will be described. FIG. 17 is a diagram illustrating a configuration example of the multidimensional table T. FIG. 18 is a graph showing the relationship between the reception window size and the transmission rate / round trip delay time in a certain wireless communication environment in CDMA 1x EV-DO.

  As shown in FIG. 18, it can be seen that even if the reception window size is increased by a certain value or more, the transmission rate is hardly improved and the round-trip delay time is increased. It can also be seen that the optimum reception window size that draws the transmission rate to the maximum and that the round-trip delay time is small is around 21900 (bytes).

  In the wireless communication environment of this figure, the predicted transmission rate and the minimum round-trip delay time were calculated to be 962 (kbps) and 100 (ms), respectively. When this value is substituted into equation (2), the calculation result is 12025 (bytes). This is significantly different from 21900 (bytes) which is the optimum reception window size. This may be due to the fact that the prediction error of the predicted transmission rate is large and that the value of the minimum round-trip delay time includes an error. As described above, it is difficult to obtain the optimum reception window size by substituting the predicted transmission rate and the minimum round-trip delay time into Equation (2).

  Evaluation by simulation shows that the optimal reception window size increases if either or both of the predicted transmission rate and the minimum round-trip delay time value increase. However, it has been found that the pattern of increase is not linear and varies with the expected transmission rate and the value of the minimum round trip delay time. It is also known that this increase pattern changes depending on the type of wireless terminal. It is difficult, if not impossible, to analyze an increase pattern of the optimal reception window size in wireless communication and to express it by a mathematical expression as in Expression (2). This is because the optimal increase pattern of the reception window size in wireless communication is not simple.

  Therefore, a multi-dimensional table T in which the predicted transmission rate and the minimum round-trip delay time and the optimal reception window size corresponding to the predicted transmission rate and the simulation are simulated and the values are plotted is created in advance. It is easier to create a multidimensional table T than to obtain a mathematical expression for obtaining an optimum reception window size, and it is possible to immediately obtain an optimum reception window size from the values of the predicted transmission rate and the minimum round-trip delay time. it can.

  As shown in FIG. 17, the multidimensional table T is a table in which the optimum reception window size is associated with the minimum round-trip delay time and the predicted transmission rate. Since the values of the multidimensional table T exist discretely, the reception window size determination unit 115 determines an intermediate value by performing an interpolation process such as linear interpolation.

(6.3) Operation of Wireless Terminal According to Fourth Embodiment Next, the operation of the wireless terminal 1 according to the fourth embodiment will be described in the order of the operation of the TCP processing unit 120 and the operation of the device driver unit 110.

(6.3.1) Operation of TCP Processing Unit FIG. 19 is a flowchart showing the operation of the TCP processing unit 120.

  In step S411, the minimum round-trip delay time notifying unit 123 notifies the device driver unit 110 of the minimum round-trip delay time stored in the minimum round-trip delay time storage unit 122. The device driver unit 110 determines the reception window size.

  In step S412, the reception window size acquisition unit 124 acquires the reception window size determined by the device driver unit 110.

  In step S413, the reception window size adjustment unit 125 compares the reception window size acquired by the reception window size acquisition unit 124 with the free space of the reception buffer at the current time.

  When the reception window size is larger than the free capacity of the reception buffer (step S413; No), in step S414, the reception window size adjustment unit 125 sets the reception window size to the same value as the free capacity of the reception buffer. This is because a larger amount of data than the free capacity of the reception buffer cannot be received.

  In step S415, the reception window size adjustment unit 125 adjusts the reception window size in order to avoid the series window syndrome. The serial window syndrome is a state in which small-sized segments are continuously transmitted.

  In step S416, the ACK generation unit 126 generates an ACK segment including information on the reception window size finally determined by the reception window size adjustment unit 125 in the header portion.

  The ACK segment generated by the ACK generation unit 126 is transmitted to the server device 400 via the network layer processing unit P3, the data link layer processing unit P2, and the physical layer processing unit P1.

(6.3.2) Operation of Device Driver Unit FIG. 20 is a flowchart showing the operation of the device driver unit 110.

  In step S <b> 421, the minimum round-trip delay time acquisition unit 111 acquires the minimum round-trip delay time notified from the TCP processing unit 120.

  In step S422, the wireless communication information acquisition unit 112 acquires wireless communication information. The predicted transmission rate calculation unit 113 calculates the predicted transmission rate by the predicted transmission rate calculation processing according to the first to third embodiments, using the wireless communication information acquired by the wireless communication information acquisition unit 112.

  In step S423, the minimum round-trip delay time acquired by the minimum round-trip delay time acquisition unit 111 and the predicted transmission rate calculated by the predicted transmission rate calculation unit 113 are input to the reception window size determination unit 115.

  In step S424, the reception window size determination unit 115 refers to the multidimensional table T, and the minimum round-trip delay time acquired by the minimum round-trip delay time acquisition unit 111 and the predicted transmission rate calculated by the predicted transmission rate calculation unit 113. From these, the optimum reception window size is determined.

  In step S425, the reception window size notification unit 116 notifies the TCP processing unit 120 of the reception window size determined by the reception window size determination unit 115.

(6.4) Effect of the Fourth Embodiment As described above, according to the fourth embodiment, the predicted transmission rate calculated by the predicted transmission rate calculation processing according to the first to third embodiments is used. By calculating the reception window size, the window size can be set appropriately.

  In the fourth embodiment, the round trip delay time measurement unit 121 notifies the device driver unit 110 of the minimum round trip delay time among the round trip delay times measured by the round trip delay time measurement unit 121 a plurality of times. As a result, the reception window size can be determined using a value close to the delay of only the link portion excluding the queue waiting delay among the delays generated in the transmission path between the wireless terminal 1 and the server apparatus 400. The window size can be set appropriately.

  Furthermore, in the fourth embodiment, by using a multidimensional table T in which values of reception window sizes obtained from evaluation experiments and simulations are plotted, an optimal reception window can be obtained from the values of the predicted transmission rate and the minimum round-trip delay time. The size can be determined immediately.

P1 ... Physical layer processing unit, P2 ... Data link layer processing unit, P3 ... Network layer processing unit, P4 ... Transport layer processing unit, P5 ... Session layer processing unit, P6 ... Presentation layer processing unit, P7 ... Application layer processing unit T ... multi-dimensional table, T1 ... definition transmission rate table, T2 ... average transmission rate table, 1 ... wireless terminal, 11 ... antenna, 12 ... radio unit, 13 ... signal processing unit, 14 ... control unit, 15 ... storage unit 16 ... Audio input / output unit, 17 ... Video input / output unit, 18 ... Operation accepting unit, 19 ... Battery, 20 ... Wireless base station, 30 ... Communication network, 40 ... Destination device, 110 ... Device driver unit, 111 ... Minimum round-trip delay time acquisition unit, 112 ... wireless communication information acquisition unit, 113 ... predicted transmission rate calculation unit, 114 ... multidimensional table storage unit, 115 ... reception window Noise determining unit 116 ... Receiving window size notifying unit 120 ... TCP processing unit 121 ... Round-trip delay time measuring unit 122 ... Minimum round-trip delay time storage unit 123 ... Minimum round-trip delay time notifying unit 124 ... Receiving window size acquisition , 125 ... reception window size adjustment unit, 126 ... ACK generation unit, 140 ... reception quality measurement unit, 141 ... DRC acquisition unit, 141C ... CQI acquisition unit, 142 ... calculation unit, 142a ... allocation rate calculation unit, 142b ... prediction Transmission rate calculation unit, 143 ... application processing unit, 145 ... average transmission rate measurement unit, 146 ... table management unit, 151 ... DRC storage unit, 151C ... CQI storage unit, 152A ... definition transmission rate storage unit, 152B ... average transmission rate Storage unit, 152C ... definition transmission rate storage unit, 153 ... allocation rate storage unit, 400 ... server device

Claims (10)

In a wireless communication system in which the modulation method of the wireless signal is dynamically switched according to the reception quality of the wireless signal received from the wireless base station via the downlink communication channel, reception at a time later than the reception time of the wireless signal A wireless terminal that predicts quality and calculates a predicted transmission rate that is a predicted value of a downlink transmission rate at the future time based on the predicted reception quality;
The reference transmission rate, which is a downlink transmission rate determined according to the predicted reception quality, and the radio within the predetermined period in all downlink communication channels that can be allocated by the radio base station within the predetermined period before the reception time. A wireless terminal comprising: a calculation unit that calculates the predicted transmission rate using an allocation rate indicating a ratio occupied by a downlink communication channel allocated to the terminal.   The calculation unit calculates a multiplication result of an average value or a maximum value of an allocation rate calculated for each predetermined period within a set period longer than the predetermined period and the reference transmission rate as the predicted transmission rate. Item 2. The wireless terminal according to Item 1. A storage unit that associates and stores an index value of either reception quality or downlink transmission rate and a defined transmission rate defined in the specifications of the wireless communication system;
The calculator is
Obtaining the defined transmission rate corresponding to the index value according to the predicted reception quality from the storage unit;
The radio terminal according to claim 1, wherein the predicted transmission rate is calculated using the acquired defined transmission rate as the reference transmission rate. A storage unit that stores an index value of either the reception quality or the downlink transmission rate and an average transmission rate based on an actual measurement value of the downlink transmission rate in association with each other;
The calculator is
Obtaining the average transmission rate corresponding to the index value according to the predicted reception quality from the storage unit;
The wireless terminal according to claim 1, wherein the predicted transmission rate is calculated using the acquired average transmission rate as the reference transmission rate. An average transmission rate measurement unit for measuring the average transmission rate;
The wireless terminal according to claim 4, wherein the storage unit stores the average transmission rate measured by the average transmission rate measurement unit in association with the index value. The storage unit stores a correspondence between the index value and the average transmission rate for each reception quality,
The calculator is
From the association according to the reception quality of the received radio signal, the average transmission rate corresponding to the index value according to the predicted reception quality is acquired from the storage unit,
The wireless terminal according to claim 4 or 5, wherein the predicted transmission rate is calculated using the acquired average transmission rate as the reference transmission rate. A measurement unit that measures a round-trip delay time between the wireless terminal and a server device that is a communication destination of the wireless terminal;
A determination unit that determines a reception window size for controlling a data transmission amount of the server device using the round trip time measured by the measurement unit and the predicted transmission rate calculated by the calculation unit; The radio | wireless terminal as described in any one of Claims 1-6 provided. The measuring unit measures the round trip delay time a plurality of times,
The determination unit determines the reception window size using a minimum round-trip delay time among round-trip delay times measured a plurality of times by the measurement unit and the predicted transmission rate calculated by the calculation unit. The wireless terminal according to claim 7. In a wireless communication system in which a modulation method of the wireless signal is dynamically switched according to reception quality of a wireless signal received by a wireless terminal from a wireless base station via a downlink communication channel, A transmission rate prediction method for predicting the reception quality at a time, and calculating a predicted transmission rate that is a predicted value of a downlink transmission rate at the future time based on the predicted reception quality,
The reference transmission rate, which is a downlink transmission rate determined according to the predicted reception quality, and the radio within the predetermined period in all downlink communication channels that can be allocated by the radio base station within the predetermined period before the reception time. A transmission rate prediction method comprising a step of calculating the predicted transmission rate using an allocation rate indicating a ratio occupied by a downlink communication channel allocated to a terminal. Measuring a round trip delay time between the wireless terminal and a server device to which the wireless terminal communicates;
Determining a reception window size for controlling the data transmission amount of the server device using the round trip time measured by the measuring step and the predicted transmission rate calculated by the calculating step; The transmission rate prediction method according to claim 9, further comprising:

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