JP4456956B2 - Wireless communication terminal, program, and communication method - Google Patents

Description

  The present invention relates to a wireless communication terminal, a program, and a communication method for performing communication by switching a plurality of communication methods.

  There is known a wireless communication terminal capable of performing communication with a base station by switching two or more communication methods. As a wireless communication terminal capable of communicating by such a plurality of communication methods, for example, two communication methods, a CDMA2000 1x system mainly using voice communication and a CDMA2000 1xEVDO system dedicated to data communication, using a common antenna, are used. There is known a wireless communication terminal that can perform communication by switching (hereinafter referred to as a dual system) (see, for example, Patent Document 1).

  In a communication system using such a dual wireless communication terminal, the CDMA2000 1xEVDO system can change the upper limit of the communication speed according to the congestion level of the base station. A wireless communication terminal in the communication system performs communication based on this upper limit. For example, as the upper limit value of the communication speed of communication from the wireless communication terminal to the base station (uplink communication), the slowest speed is selected at the start of communication. Thereafter, the wireless communication terminal changes the communication speed based on information instructing to raise or lower the upper limit value of the communication speed transmitted from the base station at every predetermined timing.

  In addition to the information transmitted from the base station at every predetermined timing, the base station may transmit urgent information for limiting the upper limit value of the communication speed to the wireless communication terminal. In this case, the wireless communication terminal changes the communication speed to the limit value based on the received urgent information. In this way, urgent information transmission is performed when, for example, a large number of wireless communication terminals are connected to one base station close to the limit of the allowable connection amount (when base stations are congested). If the base station is not dropped, the base station may go down.

  Thus, in the CDMA2000 1xEVDO system, at least the upper limit value of the communication speed in uplink communication varies.

Furthermore, in such a dual-type wireless communication terminal, if the radio wave condition between the wireless communication terminal and the base station deteriorates during communication using the CDMA2000 1xEVDO system, communication is performed using the CDMA2000 1x system, which is the other communication method. The antenna can be switched to do. By doing so, even when the wireless communication terminal determines that satisfactory communication cannot be performed in the CDMA2000 1xEVDO system due to the deterioration of the radio wave condition, the communication can be continued by switching to the CDMA2000 1x system. This switching of communication from the CDMA2000 1xEVDO system to the CDMA2000 1x system is called “hand-down”.
JP 2003-298762 A

  In the dual-type wireless communication terminal as described above, information for instructing to increase or decrease the communication speed transmitted from the base station at every predetermined timing, or information for limiting the upper limit value of the communication speed urgently transmitted from the base station Based on the above, the communication speed is changed. In this case, depending on the status of the base station, the communication speed may not increase from the start of communication (slowest speed), or once the communication speed has increased, the communication speed decreases due to an instruction for an upper limit value from the base station. The communication speed may not increase. Specifically, if the base station suddenly becomes crowded and the information instructing the base station to “decrease” the communication speed at every predetermined timing is transmitted continuously many times, it is very congested. Such as when information that restricts the communication speed is continuously transmitted due to connection to the base station.

  In such a situation, since communication at a low communication speed (for example, the slowest speed) continues, the CDMA2000 1x system is switched to the CDMA2000 1x system which is the other communication method rather than the CDMA2000 1xEVDO system. Communication with the base station is likely to improve the communication speed. However, as described above, the hand-down depends on the radio wave condition between the wireless communication terminal and the base station, and therefore cannot be handed down at an arbitrary timing. Therefore, there has been a problem that communication throughput in the CDMA2000 1xEVD system is reduced.

  Therefore, an object of the present invention is to increase the throughput of a wireless communication terminal that can communicate with a plurality of communication methods.

  According to a first aspect of the present invention, there is provided switching means for switching between a first communication method in which an upper limit value of a communication speed varies and a second communication method, and information indicating an upper limit value of the communication speed in the first communication method. A receiving means for receiving from a station, a comparing means for comparing an upper limit value received by the receiving means with a reference value determined in advance during communication with the base station in the first communication method, Control means for switching the switching means so as to perform communication in the second communication method when the upper limit value is lower than the reference value as a result of comparison by the comparison means, To do.

  According to a second aspect of the present invention, the switching means for switching between the first communication method in which the upper limit value of the communication speed varies and the second communication method, and the upper limit value of the communication speed in the first communication method are varied. Information for instructing the instruction information to lower the upper limit value of the communication speed during communication with the base station in the first communication method with receiving means for receiving instruction information to be instructed from the base station at every predetermined timing And determining means for determining whether or not the information has been received continuously for a predetermined number of times, and the instruction information for instructing to lower the upper limit value of the communication speed as a result of the determination by the determining means. Control means for switching the switching means so as to perform communication by the second communication method when continuously received for the predetermined number of times or more.

  In a third aspect based on the second aspect, the control means continuously receives the instruction information for instructing to lower the upper limit value of the communication speed as a result of the determination by the determination means for the predetermined number of times. The switching means is controlled to switch only when the upper limit value of the communication speed in the first communication method is lower than a predetermined reference value.

According to a fourth aspect, in the first or third aspect, the reference value is a value that is expected to increase a communication speed when communicating using the second communication method rather than communicating using the first communication method. The fifth invention is characterized in that, in the first invention, a derivation means for deriving an amount of remaining data to be communicated by the first communication method is provided, wherein the control means performs comparison by the comparison means. As a result, the switching control to the second communication method is performed only when the upper limit value is lower than the reference value and the remaining data amount derived by the deriving unit is larger than a predetermined amount. To do.

  According to a sixth invention, in the second invention, there is provided a derivation means for deriving an amount of remaining data to be communicated by the first communication method, and the control means determines the upper limit value of the communication speed as a result of the judgment by the judgment means The second communication is performed only when the instruction information for instructing to decrease is continuously received for the predetermined number of times or more and the remaining data amount derived by the deriving means is larger than a predetermined amount. It is characterized by switching control to a system.

  A seventh invention is a program used for a wireless communication terminal capable of performing communication by switching between a first communication method in which an upper limit value of a communication speed fluctuates and a second communication method. A first procedure for receiving information indicating an upper limit value of a communication speed in the communication method from the base station, and an upper limit received by the receiving unit at the start of communication or communication with the base station in the first communication method. When the upper limit value is lower than the reference value as a result of comparing the second procedure for comparing the value with a predetermined reference value and the comparison by the second procedure, the second procedure is started from the first communication method. And a third procedure for switching to the communication method.

  An eighth invention is a program used for a wireless communication terminal capable of performing communication by switching between the first communication method in which the upper limit value of the communication speed fluctuates and the second communication method. A first procedure for receiving instruction information from the base station at every predetermined timing to instruct to change the upper limit value of the communication speed in the communication method, and during communication with the base station in the first communication method, A second procedure for determining whether or not the instruction information is received continuously for a predetermined number of times or more, and the second procedure; When the instruction information instructing the lowering of the upper limit value of the market speed is continuously received for the predetermined number of times or more as a result of the determination by, the first communication method is switched to the second communication method. And a third procedure. And features.

  In a ninth aspect based on the eighth aspect, the third procedure includes the instruction information for instructing to lower the upper limit value of the communication speed as a result of the determination by the second procedure more than the predetermined number of times. Switching from the first communication method to the second communication method is performed only when continuous reception is performed and the upper limit value of the communication speed in the first communication method is lower than a predetermined reference value. And

  According to a tenth aspect, in the seventh or ninth aspect, the reference value is a value that is expected to increase a communication speed when communicating using the second communication method rather than communicating using the first communication method. It is characterized by being.

  An eleventh invention includes a fourth procedure for deriving an amount of remaining data to be communicated by the first communication method in the seventh invention, wherein the third procedure is a comparison of the second procedure. As a result, only when the upper limit value is lower than the reference value and the remaining data amount derived in the fourth procedure is larger than a predetermined amount, the second communication from the first communication method. It is characterized by switching to a system.

  A twelfth invention according to the eighth invention includes a fourth procedure for deriving an amount of remaining data to be communicated by the first communication method, wherein the third procedure is determined by the second procedure. As a result, the instruction information instructing to lower the upper limit value of the communication speed is continuously received for the predetermined number of times or more, and the remaining data amount derived in the fourth procedure is larger than the predetermined amount. Only in this case, the first communication method is switched to the second communication method.

  A thirteenth aspect of the present invention is a communication method for performing communication by switching between a first communication method in which an upper limit value of a communication speed fluctuates and a second communication method on a wireless communication terminal, wherein the first communication Information indicating the upper limit value of the communication speed in the system is received from the base station, and the upper limit value received from the base station and a predetermined reference value at the start or during communication with the base station in the first communication system When the upper limit value is lower than the reference value as a result of the comparison, the first communication method is switched to the second communication method.

  A fourteenth aspect of the present invention is a communication method for performing communication by switching between a first communication method in which an upper limit value of a communication speed fluctuates on a wireless communication terminal and a second communication method. Instruction information for instructing to change the upper limit value of the communication speed in the system is received from the base station at every predetermined timing, and the instruction information indicates the communication speed during communication with the base station in the first communication system. It is information for instructing to lower the upper limit value, and it is determined whether or not the information has been received continuously for a predetermined number of times. As a result of the determination, the instruction information for instructing to decrease the communication speed is When receiving continuously for a predetermined number of times or more, the first communication method is switched to the second communication method.

  According to a fifteenth aspect, in the fourteenth aspect, as a result of the determination, the instruction information instructing to reduce the communication speed is continuously received for the predetermined number of times or more, and communication in the first communication method is performed. Only when the upper limit value of the speed is lower than a predetermined reference value, the first communication method is switched to the second communication method.

  In a sixteenth aspect based on the thirteenth or fifteenth aspect, the reference value is a value that is expected to increase a communication speed when communicating using the second communication method rather than communicating using the first communication method. It is characterized by being.

  In a seventeenth aspect based on the thirteenth aspect, when the comparison result shows that the upper limit value is lower than the reference value, the amount of remaining data to be communicated in the first communication method is further derived. Only when the remaining data amount is larger than a predetermined amount, the first communication method is switched to the second communication method.

  In an eighteenth aspect based on the fourteenth aspect, when the instruction information instructing to further reduce the communication speed is received continuously for the predetermined number of times or more as a result of the determination, the first aspect The amount of remaining data to be communicated by the communication method is derived, and only when the derived amount of remaining data is larger than a predetermined amount, the first communication method is switched to the second communication method.

  ADVANTAGE OF THE INVENTION According to this invention, the throughput of the radio | wireless communication terminal which can communicate by a some communication system can be improved.

  A first embodiment of the present invention will be described below with reference to the drawings.

  FIG. 1 is a block diagram showing a configuration of radio communication terminal 200 according to the present embodiment.

  Wireless communication terminal (mobile phone terminal) 200 according to the present embodiment uses cdma2000 1x communication method (hereinafter referred to as “lx system”) and 1xEVDO communication method (hereinafter referred to as “DO system”) using common antenna 10. The wireless communication terminal can perform data communication with the base station 100A of the DO system or the base station 100B of the 1x system.

  The base station 100A performs DO system communication with the radio communication terminal 200, and the base station 100B performs 1x system communication with the radio communication terminal 200.

  The antenna 10 converts a high-frequency signal from either the 1xRF unit 20 or the DO RF unit 30 into a radio wave and transmits the radio wave to the base stations 100A and 100B, and receives a radio wave from the base stations 100A and 100B and receives the 1xRF unit 20 Alternatively, it is sent to the DO RF unit 30 as a high frequency signal.

  The 1xRF unit 20 converts data or a voice signal to be transmitted in the 1x system into a high-frequency signal and sends it to the antenna 10. Moreover, the high frequency signal sent from the antenna 10 is converted into a data signal or an audio signal.

  The DO RF unit 30 converts data to be transmitted by the DO system into a high-frequency signal and sends it to the antenna 10. Moreover, the high frequency signal sent from the antenna 10 is converted into a data signal.

  The 1 × RF unit 20 or the DO RF unit 30 functions as a receiving unit via the antenna 10.

  The RF control unit 40 is a control unit that controls communication between the two systems of the DO system and the 1x system, and functions as a switching unit described later. The system control unit 50 is a control unit that controls each unit of the wireless communication terminal 200, and the system control unit 50 functions as comparison means, control means, and derivation means described later.

  The system storage unit 60 is configured by a memory such as a RAM, and stores applications, temporary data, and the like.

  Next, fluctuations in the upper limit value of the communication speed in the data communication of the DO system of the wireless communication terminal according to the present embodiment will be described with reference to FIGS.

  First, in the uplink communication in the DO system, the upper limit value of the communication speed is divided into five stages of 9.6 kbps, 19.2 kbps, 38.4 kbps, 76.8 kbps, and 153.6 kbps. When the wireless communication terminal 200 starts uplink communication with the base station 100A, communication is first started at the lowest communication speed (9.6 kbps), and then the upper limit value of the communication speed transmitted from the base station 100A at every predetermined timing. The radio communication terminal 200 receives “RABit” (Reverse Activity Bit), which is information for instructing the increase / decrease, and adjusts the communication speed.

  RABit is a bit value that varies depending on the congestion of the base station 100A to which the wireless communication terminal 200 is connected and the peripheral base station to which the wireless communication terminal 200 is to be handed off from the base station 100A. A base station is congested when many wireless communication terminals are concentrated and connected to the base station or when a communication line is congested.

  When there is no congested base station, that is, when the communication speed can be increased, RABit is set to “0”. When there is one or more congested base stations, that is, when it is not preferable to increase the communication speed, RABit is set to “1”.

  FIG. 3 is a flowchart of communication rate change performed by the system control unit 50 of the wireless communication terminal 200.

  When the wireless communication terminal 200 starts uplink communication with the DO system, communication is first started at the lowest communication speed (9.6 kbps).

  Thereafter, when the antenna 10 receives the RABit from the base station 100A, it is determined whether or not there is a RABit indicating “1” (step 1001). When it is determined that RABit is “0”, the operation is performed to increase the upper limit value of the current communication speed by one step. In this case, the communication speed is configured to be increased probabilistically rather than absolutely. That is, first, a random number x (x is a range of 0 <x <1) is generated (step 1002). Then, it is determined whether or not the generated random number x is smaller than a threshold value α for changing the communication speed (step 1003). Here, as shown in FIG. 2, the threshold value α differs depending on the current communication speed. For example, when the threshold value α is to be increased by one step from 9.6 kbps to 19.2 kbps, the threshold value α is “0x30” (hexadecimal notation). That is, a value obtained by dividing “48” by 255, that is, 48/255 is the value of α. In this example, in step 1003, it is determined whether the random number x is larger or smaller than 48/255.

  If it is determined in step 1003 that the random number x is smaller than the threshold value α, the upper limit value of the current communication speed is increased by one level (step 1004). For example, if the current communication speed is 9.6 kbps, it is changed to 19.2 kbps, which is one step higher. On the other hand, if it is determined that the random number x is greater than or equal to the threshold value α, the upper limit value of the current communication speed is maintained (step 1005). For example, if the current communication speed is 9.6 kbps, 9.6 kbps is maintained.

  On the other hand, if it is determined in step 1001 that there is at least one base station whose RABit is “1”, the operation is performed to lower the upper limit value of the current communication speed by one step. That is, first, a random number x (x is a range of 0 <x <1) is generated (step 1006), and the random number x is compared with a threshold value α (step 1007). If it is determined that the random number x is smaller than the threshold value α, the upper limit value of the current communication speed is lowered by one step (step 1008). For example, if the current communication speed is 19.2 kbps, it is changed to 9.6 kbps, which is one step lower. On the other hand, if it is determined that the random number x is greater than or equal to the threshold value α, the upper limit value of the current communication speed is maintained (step 1005). For example, if the current communication speed is 19.2 kbps, 19.2 kbps is maintained.

  By doing in this way, the radio communication terminal 200 can change the upper limit value of the communication speed in a probabilistic and stepwise manner based on the RABit transmitted at every predetermined timing from the base station 100A.

  On the other hand, in addition to the processing of FIG. 3 using this RABit, the communication speed of the wireless communication terminal 200 may be forcibly changed by an instruction from the base station.

  In the DO system, the base station 100A may transmit a control signal called “CurrentRateLimit” separately from RABit. This CurrentRateLimit is a control signal that is urgently transmitted to the radio communication terminal 200 when the base station 100A is very congested and the throughput is significantly deteriorated. For example, when the wireless communication terminal 200 is concentrated and connected to the base station 100A near the upper limit of the number of terminals that can be connected to the base station, the base station 100A is urgently transmitted in a situation where the base station 100A may be down. .

  This CurrentRateLimit includes the above-mentioned upper limit value of the five-step communication speed, information indicating any of 9.6 kbps, 19.2 kbps, 38.4 kbps, 76,8 kbps, and 153.6 kbps, and the wireless communication that has received CurrentRateLimit Terminal 200 sets the communication speed to the upper limit value of the instructed communication speed.

  In this way, when receiving a CurrentRateLimit urgently transmitted from the base station 100A, the wireless communication terminal 200 is forcibly set to the upper limit value of the communication speed instructed by the CurrentRateLimit.

  When the radio wave state between the radio communication terminal and the base station deteriorates during communication using the DO system (for example, when the pilot signal strength (RSSI value) becomes low), The antenna can be switched so as to perform communication in the 1x system which is the communication method. By doing so, even when the wireless communication terminal determines that satisfactory communication cannot be performed in the DO system due to deterioration of the radio wave condition or the like, the communication can be continued by switching to the 1x system. This switching of communication from the DO system to the 1x system is called “hand-down”.

  For uplink communication in the 1x system, the communication speed is 9.6 kbps at the start of communication, as with the DO system, but the upper limit of the communication speed is always defined as 76.8 kbps, and the upper limit is raised or lowered step by step. Don't do that.

  Next, hand-down processing when the radio communication terminal 200 according to the first embodiment of this invention transmits a RABit from the base station 100A will be described.

  FIG. 4 is a flowchart illustrating a hand-down process performed by the system control unit 50 of the wireless communication terminal 200 according to the first embodiment of this invention.

  When the DO RF unit 30 as the receiving means receives the RABit via the antenna 10 while the wireless communication terminal 200 is performing uplink communication using the DO system, the system control unit 50 has one base station whose RABit is “1”. However, it is determined whether or not it exists (step 2001).

  If it is determined that there is at least one base station whose RABit is “1”, the system control unit 50 as a determination unit adds “1” to the variable “Y” (step 2002). This variable Y is a value indicating the cumulative number of times of continuously receiving RABits having a bit value of “1”. Next, it is determined whether or not the variable Y is greater than or equal to a predetermined threshold value m (step 2003). When it is determined that the variable Y is greater than or equal to the threshold value m, that is, when it is determined that RABits having a bit value of “1” have been continuously received a predetermined number of times (threshold value m) or more, system control as control means The unit 50 sends a command to the RF control unit 40, switches the RF control unit 40 as switching means, and executes hand-down from the DO system to the 1x system (step 2004). By doing so, communication in the 1x system starts.

  On the other hand, if it is determined in step 2001 that there is no base station with RABit “1”, the variable Y is set to the initial value “0” (step 2005), and handdown is not performed. The communication in the DO system is continued (step 2006).

  Also, as a result of the determination in step 2003, even when it is determined that the variable Y is less than the predetermined threshold value m, communication in the DO system is continued without performing hand-down (step 2006).

  After step 2004 or step 2006, the flowchart is looped back to step 2001.

  Note that the threshold value m to be compared with the variable Y, which is the cumulative number of RABit “1”, is difficult to increase for a while because the DO system is congested, so switch to the 1x system. The number of times that communication is expected to be performed at higher speed is set in advance. For example, when the threshold value m is set to “3” or “4”, a RABit of “1” is transmitted only once (traffic is concentrated on the base station 100A only for an instant). The communication in the DO system can be maintained without performing the hand-down when the RABit becomes “0” immediately after the RABit becomes “1”.

  FIG. 5 is a sequence diagram illustrating a hand-down process performed by the system control unit 50 of the wireless communication terminal 200 according to the first embodiment of this invention.

  When the radio communication terminal 200 is performing uplink communication in the DO system DO system, the base station 100A transmits the RABit, and when the DO RF unit 30 as a receiving unit receives the RABit via the antenna 10, the system control unit 50 , It is determined whether or not there is even one base station whose RABit is “1”. When it is determined that there is one or more base stations whose RABit is “1”, 1 is added to the variable Y, and it is determined whether the variable Y is greater than or equal to the threshold value m.

  If it is determined that the variable Y is greater than or equal to the threshold value m, the radio communication terminal 200 transmits a “ConnectinClose message” to the base station 100A and disconnects the DO system communication. Then, 1x-TCH (1x system traffic channel) is established with the base station 100B of the 1x system.

  After this, when uplink communication by the 1x system is completed, 1x-TCH is disconnected, and a DO-TCH (DO system traffic channel) is established with the base station 100A to return to a communicable state in the DO system. It is preferable to do so.

  As described above, when the radio communication terminal 200 according to the first embodiment of this invention receives the RABit of “1” continuously for a predetermined number of times (threshold value m) during communication in the DO system, 1 × Configured to hand down to the system. In this way, when the base station 100A is congested and communication is not possible at a satisfactory communication speed on the DO system, it is possible to give up on the upstream communication in the DO system and to expect a higher communication speed. Switch to the 1x system for communication. As a result, the uplink communication throughput can be increased.

  Next, a second embodiment of the present invention will be described.

  As in the first embodiment, the second embodiment describes a hand-down process when a RABit is transmitted from the base station 100A. The wireless communication system according to the second embodiment is common to FIG.

  FIG. 6 is a flowchart illustrating hand-down processing performed by the system control unit 50 of the wireless communication terminal 200 according to the second embodiment of this invention. Steps 2001 to 2006 are the same as the processing shown in FIG. 4 of the first embodiment, and thus the same reference numerals are given and description thereof is omitted.

  If it is determined in step 2003 that a RABit having a bit value “1” has been received continuously for a predetermined threshold value m or more, the system control unit 50 serving as a comparison unit determines the current communication speed upper limit value and the predetermined value. To determine whether the upper limit value is lower than the threshold value n (step 2007). As a result of the comparison, if it is determined that the upper limit value of the current communication speed is lower than the threshold value n, the process proceeds to step 2004, and the system control unit 50 as the control unit sends a command to the RF control unit 40 to By switching the RF control unit 40 and performing hand-down from the DO system to the 1x system, communication in the 1x system is started (step 2004).

  On the other hand, if it is determined that the upper limit value of the current communication speed is equal to or greater than the threshold value n as a result of the comparison in step 2007, communication in the DO system is continued without performing hand-down (step 2006).

  Note that the threshold value n is set in advance to a communication speed that is assumed to be able to be communicated at high speed when communication is performed by switching from the DO system to the 1x system. For example, the upper limit (76.8 kbps) of the uplink communication speed of the 1x system may be set to the value n.

  As described above, the wireless communication terminal 200 according to the second embodiment of the present invention continuously receives the RABit of “1” during the communication with the DO system for a predetermined number of times (threshold value m) or more. The hand-down is configured only when the upper limit value of the communication speed is lower than a predetermined threshold value n. By doing so, the following effects can be obtained. That is, as described above in the first embodiment, even when RABit is “1”, the random number x is generated and compared with the threshold value α. Therefore, even if RABit indicating “1” is received a predetermined number of times Y or more, if the acquired random number x exceeds the threshold value α, the upper limit value of the communication speed does not decrease. Even when the RABit indicating “1” is received as described above, if the upper limit value of the actual communication speed is not lowered, the communication can be performed at a higher speed by continuing the communication using the DO system. In this embodiment, the upper limit value of the actual communication speed is compared with a predetermined threshold value n, and hand-down is performed only when the actual communication speed becomes low, and the upper limit value of the DO system communication speed is sufficiently high. In this case, communication is continued with the DO system without handing down to the 1x system. As a result, the uplink communication throughput can be increased.

  Next, a third embodiment of the present invention will be described.

  As in the first embodiment, the third embodiment describes a hand-down process when a RABit is transmitted from the base station 100A. The wireless communication system according to the third embodiment is the same as that shown in FIG.

  FIG. 7 is a flowchart illustrating a hand-down process performed by the system control unit 50 of the wireless communication terminal 200 according to the third embodiment of this invention. Since steps 2001 to 2007 are the same as the processes shown in FIGS. 4 and 6 of the first and second embodiments, the same reference numerals are given and description thereof is omitted.

  As a result of the comparison in step 2007, if it is determined that the upper limit value of the current communication speed is lower than the threshold value n, then the system control unit 50 as a derivation unit refers to, for example, a buffer in the system storage unit 60. Thus, the data amount of the data that is the target of the uplink communication is derived. Then, it is determined whether or not the derived data amount is greater than or equal to a predetermined threshold value β (step 2008). As a result of the determination, if the derived data amount is equal to or larger than the threshold value β, the system control unit 50 as the control unit sends a command to the RF control unit 40, switches the RF control unit 40 as the switching unit, and The hand-down is executed from 1 to the 1x system, and communication in the 1x system is started (step 2004).

  On the other hand, as a result of the determination in step 2008, when it is determined that the derived data amount is less than the threshold value β, communication in the DO system is continued without performing hand-down (step 2006).

  Note that the predetermined threshold β is set in advance to a data amount that is assumed to be more efficiently communicated by handing down to the 1 × system because the DO system is congested. In this case, it may be determined by comparing the total amount of data to be transmitted with the threshold β, or the untransmitted data amount obtained by subtracting the amount of data that has already been transmitted from the total amount to be transmitted and the threshold β You may judge by comparing.

  As described above, the wireless communication terminal 200 according to the third embodiment of the present invention receives the RABit that is “1” continuously during the communication with the DO system, as a result of continuously receiving a predetermined number of times (threshold m). When the upper limit value of the communication speed is lower than a predetermined threshold value n, the DO system is configured to hand down from the DO system to the 1x system only when it is determined that data greater than the predetermined threshold value β is transmitted. By doing so, the following effects can be obtained. That is, a certain amount of processing time occurs in the process of handing down from the DO system to the 1x system, but even if the upper limit of the communication speed of the DO system is somewhat low, a small amount of data that can be transmitted in a short time is obtained. In the case of transmission, if it is handed down to the 1x system, it takes time for the hand-down process, and it may take a longer total time to complete transmission of all data than in the case of not handing down. In the present embodiment, when the amount of data is so small that it is desirable not to perform hand-down, communication is continued in the DO system without hand-down to the 1x system. As a result, the uplink communication throughput can be increased.

  Next, a fourth embodiment of the present invention will be described.

  In the fourth embodiment, a hand-down process when CurrentRateLimit is transmitted from the base station 100A will be described. The wireless communication system according to the fourth embodiment is the same as that shown in FIG.

  FIG. 8 is a flowchart illustrating a hand-down process performed by the system control unit 50 of the wireless communication terminal 200 according to the fourth embodiment of this invention.

  When the DO RF unit 30 serving as the receiving unit receives CurrentRateLimit via the antenna 10 while the wireless communication terminal 200 is performing uplink communication using the DO system, the system control unit 50 serving as the comparing unit determines the communication speed indicated by the CurrentRateLimit. The upper limit value is compared with a predetermined threshold value n (step 3001). As a result of the comparison, when it is determined that the upper limit value of the communication speed indicated by CurrentRateLimit is lower than the predetermined threshold value n, the system control unit 50 as the control unit sends a command to the RF control unit 40, and the RF as the switching unit The controller 40 is switched to perform hand-down from the DO system to the 1x system, and communication in the 1x system is started (step 3002).

  On the other hand, as a result of the determination in step 3002, if it is determined that the upper limit value of the communication speed indicated by CurrentRateLimit is higher than the predetermined threshold value n, communication in the DO system is continued without performing hand-down (step 3003). .

  Note that the threshold value n for comparing the communication speeds indicated by CurrentRateLimit is set in advance to a communication speed that is assumed to be higher if communication is performed after switching to the 1x system. For example, the upper limit (76.8 kbps) of the uplink communication speed of the 1x system may be set to the value n.

  FIG. 9 is a sequence diagram illustrating a hand-down process performed by the system control unit 50 of the wireless communication terminal 200 according to the fourth embodiment of this invention.

  When the radio communication terminal 200 is performing uplink communication with the DO system, the base station 100A transmits CurrentRateLimit, and when the DO RF unit 30 as a receiving unit receives the CurrentRateLimit via the antenna 10, the system control unit 50 indicates the CurrentRateLimit instruction. The upper limit value of the communication speed to be compared is compared with a predetermined threshold value n. As a result of the comparison, when it is determined that the upper limit value of the communication speed indicated by CurrentRateLimit is lower than the predetermined threshold value n, the wireless communication terminal 200 transmits a “ConnectinClose Message” to the base station 100A to communicate with the DO system. Disconnect. Then, 1x-TCH (1x system traffic channel) is established with the base station 100B of the 1x system.

  After this, when uplink communication by the 1x system is completed, 1x-TCH is disconnected, and a DO-TCH (DO system traffic channel) is established with the base station 100A to return to a communicable state in the DO system. It is preferable to do so.

  As described above, when the wireless communication terminal 200 according to the fourth embodiment of the present invention receives CurrentRateLimit indicating a communication speed lower than a predetermined communication speed (threshold value n) during communication in the DO system. Configured to hand down to a 1x system. In this way, when the base station 100A is extremely congested and cannot communicate at a satisfactory communication speed, the DO system is given up and a 1x system that can be expected to have a higher communication speed can be realized. Switch to communicate. As a result, the uplink communication throughput can be increased.

  Next, a fifth embodiment of the present invention will be described.

  As in the fourth embodiment, the fifth embodiment describes a hand-down process when CurrentRateLimit is transmitted from the base station 100A. The wireless communication system according to the fifth embodiment is the same as that shown in FIG.

  FIG. 10 is a flowchart illustrating a hand-down process performed by the system control unit 50 of the wireless communication terminal 200 according to the fifth embodiment of this invention. Note that steps 3001 to 3003 are the same as the processing shown in FIG. 8 of the fourth embodiment, and thus the same reference numerals are given and description thereof is omitted.

  If it is determined as a result of the comparison in step 3001 that the upper limit value of the communication speed indicated by CurrentRateLimit is lower than a predetermined threshold value n, then the system control unit 50 as a derivation unit, for example, in the system storage unit 60 By referring to the buffer, the amount of data that is the object of uplink communication is derived. Then, it is determined whether or not the derived data amount is greater than or equal to a predetermined threshold value β (step 3004). As a result of the determination, if the derived data amount is equal to or larger than the threshold value β, the system control unit 50 as the control unit sends a command to the RF control unit 40, switches the RF control unit 40 as the switching unit, and The hand-down is executed from 1 to the 1x system, and communication in the 1x system is started (step 3002).

  On the other hand, as a result of the determination in step 3004, if it is determined that the derived data amount is less than the threshold value β, communication in the DO system is continued without performing hand-down (step 3003).

  Note that the predetermined threshold β is set in advance to a data amount that is assumed to be more efficiently communicated by handing down to the 1 × system because the DO system is congested. In this case, determination may be made by comparing the total amount of data to be transmitted with the threshold β, or the amount of untransmitted data obtained by subtracting the amount of data already transmitted from the total amount to be transmitted and the base β You may judge by comparing.

  As described above, when the wireless communication terminal 200 according to the fifth embodiment of the present invention receives CurrentRateLimit indicating a communication speed lower than a predetermined communication speed (threshold value n) during communication in the DO system. In addition, the DO system is configured to be handed down to the 1 × system only when it is determined to transmit data of a predetermined threshold value β or more. By doing so, the following effects can be obtained. That is, a certain amount of processing time occurs in the process of handing down from the DO system to the 1x system, but even if the upper limit of the communication speed of the DO system is somewhat low, a small amount of data that can be transmitted in a short time is obtained. In the case of transmission, if it is handed down to the 1x system, it takes time for the hand-down process, and it may take a longer total time to complete transmission of all data than in the case of not handing down. In the present embodiment, when the amount of data is so small that it is desirable not to perform hand-down, communication is continued in the DO system without hand-down to the 1x system. As a result, the uplink communication throughput can be increased.

  In the fourth and fifth embodiments, the case where CurrentRateLimit is received during communication in the DO system has been described. However, the present invention can also be applied to the case where CurrentRateLimit is received at the start of communication in the DO system.

  The first to fifth embodiments of the present invention described above are all 1x systems that can be expected to perform higher-speed communication if the DO communication speed of the DO system is low and satisfactory throughput cannot be obtained. Since communication is performed by switching, the throughput of the wireless communication terminal 200 can be increased. Note that any one of the first to fifth embodiments may be combined. That is, when the radio communication terminal 200 receives RABit, the process of FIG. 4 of the first embodiment is performed, and when the radio communication terminal 200 receives CurrentRateLimit, the process of the fourth embodiment is performed. A configuration in which the processing of FIG. 8 is performed may be employed.

  In the embodiment of the present invention, the pilot signal strength (RSSI value) is used to determine the radio wave condition with the base station, but this is used using the carrier-to-interference wave ratio (C / I value) of the pilot signal. Also good.

  In the embodiment of the present invention, the hybrid system of the CDMA2000 1x system and the CDMA2000 1xEVDO system has been described. However, the present invention is not limited to this, and communication is possible using two or more communication systems. As long as data communication is performed using one communication method by switching to the other communication method and data communication is performed by switching the communication method to the other communication method, the type of communication method is not limited.

It is a block diagram showing the structure of the radio | wireless communication terminal of the 1st Embodiment of this invention. It is a table | surface which shows the relationship between the change of the communication rate of 1st Embodiment of this invention, and threshold value (alpha). It is a flowchart of the communication rate change of the 1st Embodiment of this invention. It is a flowchart which shows the hand-down process of the 1st Embodiment of this invention. It is a sequence diagram which shows the hand-down process of the 1st Embodiment of this invention. It is a flowchart which shows the hand-down process of the 2nd Embodiment of this invention. It is a flowchart which shows the hand down process of the 3rd Embodiment of this invention. It is a flowchart which shows the hand-down process of the 4th Embodiment of this invention. It is a sequence diagram which shows the hand down process of the 4th Embodiment of this invention. It is a flowchart which shows the hand down process of the 5th Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Antenna 20 1xRF part 30 DO RF part 40 RF control part 50 System control part 60 System storage part 100A, 100B Base station 200 Wireless communication terminal

Claims (18)

A switching means for switching between the first communication method in which the upper limit value of the communication speed fluctuates and the second communication method;
Receiving means for receiving information indicating an upper limit value of a communication speed in the first communication method from a base station;
Comparing means for comparing an upper limit value received by the receiving means with a predetermined reference value at the time of starting communication or communicating with the base station in the first communication method;
Control means for switching control of the switching means so as to perform communication in the second communication method when the upper limit value is lower than the reference value as a result of comparison by the comparison means. A wireless communication terminal. A switching means for switching between the first communication method in which the upper limit value of the communication speed fluctuates and the second communication method;
Receiving means for receiving, from the base station, instruction information for instructing to change the upper limit value of the communication speed in the first communication method;
During communication with the base station in the first communication method, the instruction information is information for instructing to lower the upper limit of the communication speed, and whether or not the information has been received continuously for a predetermined number of times. A judging means for judging whether or not
As a result of the determination by the determination means, when the instruction information instructing to lower the upper limit value of the communication speed is continuously received for the predetermined number of times or more, the communication is performed by the second communication method. Control means for switching control of the switching means;
A wireless communication terminal comprising:   The control means continuously receives the instruction information for instructing to lower the upper limit value of the communication speed as a result of the determination by the determination means, and the communication speed in the first communication method 3. The wireless communication terminal according to claim 2, wherein the switching unit is controlled to switch only when the upper limit value is lower than a predetermined reference value. 4.   4. The reference value according to claim 1 or 3, wherein the reference value is a value that is expected to increase a communication speed when communicating by the second communication method than by communicating by the first communication method. Wireless communication terminal.   Deriving means for deriving the amount of remaining data to be communicated in the first communication method is provided, and the control means obtains the upper limit value lower than the reference value as a result of comparison by the comparing means, and the deriving means derives 2. The wireless communication terminal according to claim 1, wherein switching to the second communication method is controlled only when the remaining data amount is greater than a predetermined amount.   Derivation means for deriving the amount of remaining data to be communicated in the first communication method, the control means, as a result of the determination by the determination means, the instruction information for instructing to lower the upper limit value of the communication speed in advance The switching control to the second communication method is performed only when the data is continuously received a predetermined number of times or more and the remaining data amount derived by the deriving unit is larger than a predetermined amount. 2. A wireless communication terminal according to 2. A program used for a wireless communication terminal capable of performing communication by switching between a first communication method in which an upper limit value of a communication speed fluctuates and a second communication method,
A first procedure for receiving, from a base station, information indicating an upper limit value of a communication speed in the first communication method;
A second procedure for comparing an upper limit value received by the receiving means with a predetermined reference value at the start of communication or during communication with the base station in the first communication method;
As a result of the comparison by the second procedure, when the upper limit value is lower than the reference value, a third procedure for switching from the first communication method to the second communication method;
The program characterized by comprising. A program used for a wireless communication terminal capable of performing communication by switching between a first communication method in which an upper limit value of a communication speed fluctuates and a second communication method,
A first procedure for receiving, from the base station, instruction information for instructing to change the upper limit value of the communication speed in the first communication method at a predetermined timing;
During communication with the base station in the first communication method, the instruction information is information for instructing to lower the upper limit of the communication speed, and whether or not the information has been received continuously for a predetermined number of times. A second procedure for determining whether or not
As a result of the determination by the second procedure, when the instruction information for instructing to lower the upper limit value of the value rate is continuously received for the predetermined number of times or more, the second communication method starts from the first communication method. A third procedure for switching to the communication method of
The program characterized by comprising.   In the third procedure, as a result of the determination in the second procedure, the instruction information instructing to lower the upper limit value of the communication speed is continuously received for the predetermined number of times, and the first communication is performed. 9. The program according to claim 8, wherein the program is switched from the first communication method to the second communication method only when the upper limit value of the communication speed in the method is lower than a predetermined reference value.   10. The reference value according to claim 7 or 9, wherein the reference value is a value that is expected to increase a communication speed when communicating with the second communication method rather than communicating with the first communication method. Program. Including a fourth procedure for deriving an amount of remaining data to be communicated in the first communication method;
In the third procedure, as a result of the comparison in the second procedure, the upper limit value is lower than the reference value, and the remaining data amount derived in the fourth procedure is larger than a predetermined amount. The program according to claim 7, wherein only the first communication method is switched to the second communication method. Including a fourth procedure for deriving an amount of remaining data to be communicated in the first communication method;
In the third procedure, as a result of the determination by the second procedure, the instruction information instructing to lower the upper limit value of the communication speed is continuously received for the predetermined number of times, and the fourth procedure is performed. 9. The program according to claim 8, wherein the program is switched from the first communication method to the second communication method only when the remaining data amount derived in (1) is larger than a predetermined amount. A communication method for performing communication by switching between a first communication method in which an upper limit value of a communication speed fluctuates and a second communication method on a wireless communication terminal,
Receiving information indicating the upper limit of the communication speed in the first communication method from the base station;
During the start of communication with the base station in the first communication method or during communication, the upper limit value received from the base station is compared with a predetermined reference value,
As a result of the comparison, when the upper limit value is lower than the reference value, the first communication method is switched to the second communication method.
A communication method characterized by the above. A communication method for performing communication by switching between a first communication method in which an upper limit value of a communication speed fluctuates and a second communication method on a wireless communication terminal,
Receiving instruction information for instructing to change the upper limit of the communication speed in the first communication method from the base station at every predetermined timing;
During communication with the base station in the first communication method, the instruction information is information for instructing to lower the upper limit of the communication speed, and whether or not the information has been received continuously for a predetermined number of times. Determine whether
As a result of the determination, when the instruction information instructing to reduce the communication speed is continuously received for the predetermined number of times or more, the first communication method is switched to the second communication method.
A communication method characterized by the above.   As a result of the determination, the instruction information instructing to lower the communication speed is continuously received for the predetermined number of times or more, and the upper limit value of the communication speed in the first communication method is lower than a predetermined reference value. The communication method according to claim 14, wherein the communication method is switched from the first communication method to the second communication method only when it is low.   16. The reference value according to claim 13 or 15, wherein the reference value is a value that is expected to increase a communication speed when communication is performed using the second communication method rather than communication using the first communication method. Communication method.   As a result of the comparison, when the upper limit value is lower than the reference value, the amount of remaining data communicated by the first communication method is further derived, and the derived remaining data amount is larger than a predetermined amount 14. The communication method according to claim 13, wherein only the first communication method is switched to the second communication method.   As a result of the determination, when the instruction information for instructing to further reduce the communication speed is continuously received for the predetermined number of times or more, an amount of remaining data to be communicated in the first communication method is further derived. The communication method according to claim 14, wherein the first communication method is switched to the second communication method only when the derived remaining data amount is larger than a predetermined amount.

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